Golang: generating core failed: unable to load github.com - go

Question

I installed golang and started with this tutorial: https://www.howtographql.com/graphql-go/1-getting-started/
When I run:
go run github.com/99designs/gqlgen generate
I get:
reloading module info
generating core failed: unable to load github.com/my-user/hackernews/graph/model - make sure you're using an import path to a package that exists
exit status 1
What is wrong with my setup?
This is my gopath
/Users/my-pc-user/go

Answer 1

TLDR
$ cd your_project_path/
$ print '// +build tools\npackage tools\nimport _ "github.com/99designs/gqlgen"' | gofmt > ./tools.go
$ echo 'package model' | gofmt > ./graph/model/doc.go
$ go get .
Explanation
According to a quick start guide, you should create a package with generated code that actually is already imported by your server:
package main
import (
"log"
"net/http"
"os"
"github.com/99designs/gqlgen/graphql/handler"
"github.com/99designs/gqlgen/graphql/playground"
"your_module_name/graph"
"your_module_name/graph/generated"
)
Because of the fact that your_module_name/graph/generated has no *.go files you cannot start a server and if you try you will get an error like:
graph/schema.resolvers.go:10:2: no required module provides package your_module_name/graph/generated; to add it:
To generate that package you will need to execute go run github.com/99designs/gqlgen generate, but there is another problem: gqlgen generates code that uses another package that is still doesn't exist yet, i.e. your_module_name/graph/model.
Additional step adding build constraints is required to not drop indirect dependency while generation process. That's why there is the first step with underscore import.
And if you put any *.go file to that directory with package directive — everything should works now:
$ cd your_project_path/
$ print '// +build tools\npackage tools\nimport _ "github.com/99designs/gqlgen"' | gofmt > ./tools.go
$ echo 'package model' | gofmt > ./graph/model/doc.go
$ go get .