For a contrived example:
I have 2 packages, repo.com/alpha/A & repo.net/beta/B. package A uses package B, both structured as example.
A:
main.go
B:
b.go
templates \
1.tmpl
2.tmpl
In main.go of package A, I'd need to access the templates directory of package B.
b.go
var templates string
templates = templatepath
func init(){
templatepath, _ = filepath.Abs("./templates")
}
main.go
import(
repo.net/beta/B
)
func main(){
fmt.Printf("%s", B.templates)
}
So the problem being in my more complex use case & the contrived example here is that B.templates will be in the directory for package A, where I need to establish and reference the directory of the imported path. This is part of learning and navigating the Go way of doing things, and my understanding is probably basic, so I need to understand how to do this in a Go context.
My use case is a package that uses other packages that do things for the base package, and these external packages may use standard web resources files(css, html, js) the problem being I'm having immediate trouble packaging and referencing them abstractly enough for what I want to do.
You can't, you have to either use something like go-bindata or so, or simply embed the templates in your B package as consts.
tmpl1.go:
const tmpl1 = `........`
Related
My current Directory is setup as follows:
-- /webserver
|
/ftp
|-> ftp.go
|-> go.mod
|->server.go
|->go.mod
Server.go page heading
package main
import (
[..]
"../webserver/ftp" // issue package
)
func main() {
[..]
ftp.test()
}
ftp.go page
package ftp
import "fmt"
func test() {
fmt.Println("YES!")
}
Here's the part I cant seem to understand in the console "PROMBLEMS" tab. The ftp.go file gets saved. Before I save the server.go file with "../webserver/ftp/" the console displays this:
When I save server.go it removes "./webserver/ftp", I went as far as adding it into the go src to make it "ftp" instead of "../webserver/ftp". I get the same result.
Not sure what I am doing wrong.
Basically what i want to accomplish is:
have a functions folder and have the functions in that folder (functions.go) to keep the server.go page as clean as possible.
You have several problems here.
ftp/go.mod should not exist. While it is possible to have multiple Go modules in a single repository, this is very advanced usage, and is rarely useful. Unless you absoultely know that you need this capability, and are already exremely comfortable with creating and publishing Go modules, don't do this.
Go does not support relative imports. import "../webserver/ftp" is an invalid import path*. Use the fully qualified import path, i.e. import "github.com/username/projectname/webserver/ftp"
The path to use here depends on the module name you've declared on the module line of your your top-level go.mod file.
You cannot import unexported values.
You've defined func test() string in ftp.go. This is unexported, by virtue of beginning with a lowercase letter. Only functions, variables, or other symbols which begin with a capital letter are exported in Go. Try func Test() string instead.
*Some will say "But I used import ".../foo" and it worked!". Yes, it can work under very specific circumstances. But its behavior is not reliable, so you should never rely on this, except in very specific testing types of situations.
Goal: I want to reuse many Go functions from two Go functions with HTTP triggers.
What I have tried and steps to reproduce the problem:
In GCP, create a new Go 1.11 Cloud Function, HTTP Trigger
Name it: MyReusableHelloWorld
In function.go, paste this:
package Potatoes
import (
"net/http"
)
// Potatoes return potatoes
func Potatoes(http.ResponseWriter, *http.Request) {
}
In go.mod, paste this: module example.com/foo
In function to execute, paste this: Potatoes
Click on deploy. It works.
Create another Go serverless function in GCP
In function. go, paste this:
// Package p contains an HTTP Cloud Function.
package p
import (
"encoding/json"
"fmt"
"html"
"net/http"
"example.com/foo/Potatoes"
)
// HelloWorld prints the JSON encoded "message" field in the body
// of the request or "Hello, World!" if there isn't one.
func HelloWorld(w http.ResponseWriter, r *http.Request) {
var d struct {
Message string `json:"message"`
}
if err := json.NewDecoder(r.Body).Decode(&d); err != nil {
fmt.Fprint(w, "error here!")
return
}
if d.Message == "" {
fmt.Fprint(w, "oh boy Hello World!")
return
}
fmt.Fprint(w, html.EscapeString(d.Message))
}
In go.mod, paste this: module example.com/foo
In function to execute, paste this: HelloWorld
Click on deploy. It doesn't work. You have the error: unknown import path "example.com/foo/Potatoes": cannot find module providing package example.com/foo/Potatoes
I have also tried all kinds of combinations for the module/packages to import.
I have tried without the example.com/ part.
Other smaller issue:
The functions I want to reuse could all be in the same file and don't really need any trigger, but it doesn't seem that having no trigger is possible.
Related questions and documentation with which I could not achieve my goal:
How can I use a sub-packages with Go on Google Cloud Functions?
https://github.com/golang/go/wiki/Modules , section go.mod
You can’t invoke a cloud function from another one, because each function is in its own container independently.
So If you want to deploy the function with a dependency that can't be downloaded from a package manager you need to put the code together like here and deploy using the CLI
It is likely each cloud function defined in the console is independent of the other. If you want code reuse, it's best to structure it as per the following document and deploy it using gcloud command.
https://cloud.google.com/functions/docs/writing/#structuring_source_code
You are mixing things: package management and function deployment.
When you deploy a Cloud Function, if you want to (re)use it, you have to call if with http package.
If you build a package that you want to include in your source code, you have to rely on package manager. With Go, Git repository, like Github, is the best way to achieve this (Don't forget to perform a release and to name it as expected by Go mod: vX.Y.Z)
Here your code can't work without more engineering and package publication/management.
I achieve the same things but with a Dockerfile and I deplored my code in Cloud Run (that I recommend you if you aren't event oriented and only HTTP oriented. I wrote a comparison on Medium)
Root
go.mod
pkg/foo.go
pkg/go.mod
service/Helloworld.go
service/go.mod
In my helloworld.go, I can reuse the package foo. For this I perform this in my service/go.mod file
module service/helloworld
go 1.12
require pkg/foo v0.0.0
replace pkg/foo v0.0.0 => ../pkg
Then when you build your container, you run your go build service/Helloworld.go from the root directory.
I want to move code used by a specific subdomain its own project, which will be imported by the main code base which is currently resides in. I am able to import code from the subdomain into the main project successfully, until I add the Gorilla Mux code. For example, this works:
// imports and non-relevant routes removed for simplicity
r := mux.NewRouter()
// Primary site routes here...
s := r.Host("subdomain-regex-here").Subrouter()
s.HandleFunc("/", people.Index)
http.ListenAndServe("localhost:8080", r)
But when I move the subdomain to its own project and import it, then call the LoadRoutes() function which passes in the mux.Router object from the primary site, I receive an error. Here's the code:
// Primary Project
r := mux.NewRouter()
// Primary site routes here...
// function located in the subdomain go project, which is imported
func LoadRoutes(host string, r *m.Router) {
s := r.Host(host).Subrouter()
s.HandleFunc("/", people.Index)
s.HandleFunc("/people", people.Index)
s.HandleFunc("/person/new", people.New)
}
# command-line-arguments
./main.go:25: cannot use r (type *"primary_site/vendor/github.com/gorilla/mux".Router) as type *"subdomain_site/vendor/github.com/gorilla/mux".Router in argument to routers.LoadRoutes
It looks like I have two instances of the Gorilla Mux, from two separate projects, that are conflicting. I only import packages from the subdomain site to the primary site, not the other way around. This exact code works perfectly as long as I have it in a single project, but when I try to separate the projects, it breaks.
Since I pass in the instance of mux.NewRouter(), why am I having a conflict?
You have 2 vendor directories in your project. You need to flatten them into a single vendor directory at the top level in order to share vendored types between packages. Remove the subdomain_site/vendor and only use the vendor directory in your main pacakage.
I am using a golang package, say name pkgfoo; and the author explicitly said if we want to use a package subpkg under pkgfoo, I need to explicitly import subpkg. I don't understand the reason behind it. Isn't the subpkg automatically imported if I import the top pkg in Golang?
package main
import (
"myownpackage"
"github.com/usera/pkgfoo"
"github.com/usera/pkgfoo/subpkg"
)
func main() {
// Use functions in pkgfoo, and use functions in pkgfoo/subpkg
// ......
http.HandleFunc("/login", login)
err := http.ListenAndServe(":9090", nil) // setting listening port
if err != nil {
log.Fatal("ListenAndServe: ", err)
}
}
My question is whether I really need import "github.com/usera/pkgfoo/subpkg" statement.
Go packages are constructed from one or more source files, which are organized into folders in the file system. Source files of the same package must be in the same folder.
But in Go there is no "package hierarchy", the "subpackage" term simply refers to the folder of a package being a subfolder of another. We often organize packages to be in folders being subfolders of others because there is some connection between those packages (e.g. a package is used only by another being in the parent folder; or a package in a subfolder is a specific or more special implementation of the package in the parent folder; or simply just a logical grouping - see the end of the answer).
So whenever you do
import "github.com/usera/pkgfoo"
It only imports pkgfoo and no other packages sharing the same path as prefix. If you need github.com/usera/pkgfoo/subpkg too, you also need to explicitly import it:
import (
"github.com/usera/pkgfoo"
"github.com/usera/pkgfoo/subpkg"
}
The Go Blog: Package names on directories used in the standard library:
Directories. The standard library uses like directories crypto, container, encoding, and image to group packages for related protocols and algorithms. There is no actual relationship among the packages in one of these directories; a directory just provides a way to arrange the files. Any package can import any other package provided the import does not create a cycle.
I am using wgo for dependency management in Golang (although I think wgo has little to do with this), wgo has a folder structure like this
project/
.gocfg/
gopaths
vendor.json
vendor/
src/
github.com_or_whatever/
I have a library I coded myself which uses an nsq-go type in one of the exported methods:
func AddNsqSubscription(
topic, channel string,
handler nsq.Handler,
config *nsq.Config) error { }
The library is called messi and I import the nsq-go like so "messi/vendor/src/github.com/bitly/go-nsq"
The problem comes when I try to use this library in another project. For instance, in a project called scribe I have the following code (notice the imports):
import (
"scribe/vendor/src/github.com/bitly/go-nsq"
"scribe/vendor/src/messi"
)
//...
nsqHandler := nsq.HandlerFunc(func(message *nsq.Message) error {
msgHandler(MessiMessage{message})
return nil
})
return messi.AddNsqSubscription(destination, subdestination, nsqHandler, nsq.NewConfig())
When I go build the following error is returned:
cannot use nsqHandler (type "scribe/vendor/src/github.com/bitly/go-nsq".HandlerFunc) as type "messi/vendor/src/github.com/bitly/go-nsq".Handler in argument to messi.AddNsqSubscription:
"scribe/vendor/src/github.com/bitly/go-nsq".HandlerFunc does not implement "messi/vendor/src/github.com/bitly/go-nsq".Handler (wrong type for HandleMessage method)
have HandleMessage("scribe/vendor/src/github.com/bitly/go-nsq".Message) error
want HandleMessage("messi/vendor/src/github.com/bitly/go-nsq".Message) error
Why? I do not really know what is going on. The code go-nsq imported is exactly the same, yet golang wants that this code comes from the same folder?
What am I doing wrong?
Packages in Go are identified by full import path, not by name.
For example in the standard library there are two different packages with the same name template but different import paths: text/template and html/template.
You should make sure that go-nsq package is imported using the same path.