How to load local assets within a GCP cloud function? - go

Question

I'm building a tiny GCP cloud function in Golang that returns a generated PNG file when calling it via HTTP. I deployed my code via ZIP-Upload in the Google Cloud Console.
Currently it gets called properly and the code gets compiled etc. But in my code I have to load several local files - a font and a .png image.
I bundled those in the ZIP I uploaded and the files are visible in the Source-View in GCP. All files (images, fonts and go-files) are within the same directory.
When calling the cloud function the log states the following:
2019/01/21 14:59:31 open /english.png: no such file or directory
I tried to change the way i build the path to the file in go. I already used /german.png statically, used several attempts to build the path dynamically.
I'm not 100 percent sure if this is the way to go, but it is my first experiment with "serverless" and i am willing to get it done the "right" way.
import "github.com/fogleman/gg"
func main() {
ex, err := os.Executable()
if err != nil {
panic(err)
}
executableDir := filepath.Dir(ex)
img, err :=gg.LoadPNG(path.Join(executableDir, "./english.png"))
if err != nil {
log.Fatal(err)
}
}
Currently the file can not be found in any attempt i made. Maybe the path the images get "deployed" into are different from the ones i tried - i have not found any note on that in the documentation.
I'd obviously expect it to be loaded properly.

Answer 1

For the Go 1.13 according to the documentation, as of today (Jul 2020), source code is located in the ./serverless_function_source_code directory.
A good reference to follow is the buildpack.

Answer 2

I created http functions with the following structure:
api
|--test.txt
|--api.go
And wrote simple function to reply with file content:
package api
import (
"io/ioutil"
"net/http"
)
// FileTest func
func FileTest(w http.ResponseWriter, r *http.Request) {
content, err := ioutil.ReadFile("./test.txt")
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
w.Write([]byte(err.Error()))
return
}
w.Write(content)
}
It returns the file content without any problems. https://us-central1-clickshield24m.cloudfunctions.net/api
So in your case I would try change the path to gg.LoadPNG("./english.png")

Answer 3

./serverless_function_source_code didn't work for me using go113 runtime with vendoring. I wanted to locate a file in the vendor directory.
My file structure is:
myfn
|- main.go
|- go.mod
|- .gcloudignore
My deployment steps are:
cd myfn
go mod vendor
gcloud functions deploy MyFunction --runtime go113 --set-env-vars "PATH_FILES=./src/myfn/vendor/static"
I found this out by deploying a function that listed all files to a certain depth starting with "." and didn't see a serverless_function_source_code directory. But there was src/myfn.