Include and Find Files Included in Go Function

Question

I’ve searched through the documentation to the best of my ability, and can’t find anything that helps me understand how to simply include a 200kb .jpg file in with my function.

I’m creating a Go Function that needs to use a base image for creating a new modified image based on some parameters. I’d like to have it somewhere on disk that my function can simply use it load it to a buffer, modify the buffer, return the buffer as an image response.

Based on the docs, it seems everything around my go code should be zipped up and in the container. I’ve done some looking, and I can’t seem to find where my image is landing (or even if it’s being included at all).

I do not have an ignore file, nor an include. I’ve tried an include, but still could not find it during runtime.

My project is essentially:

Root
.Packages
..image-func
...code.go
...base.jpg

My temporary solution will be to download it at runtime, and attempt to cache it in /tmp to promote reuse; but this is annoying and I need to maintain hosting the image somewhere independently from my source.

Any information/more specifics on the go build would be greatly appreciated.

Matt Welke · Accepted Answer

For Go functions, the approach we recommend for including arbitrary files alongside deployed function code is to use Go’s embed package. You’re right that right now, our docs don’t cover this. Thanks for posting this to let us know. We’re going to update our documentation to include this.

In the mean time, here’s an example for your use case. It embeds a PNG image file. I took one of the images from one of our blog posts, sammy-jetpack.png.

My directory structure:

.
├── packages
│   └── go-embed-image-example
│       └── fn
│           ├── main.go
│           └── sammy-jetpack.png
└── project.yml

My project.yml file:

packages:
  - name: go-embed-image-example
    functions:
    - name: fn
      runtime: go:1.20

My main.go file:

package main

import (
    _ "embed"
    b64 "encoding/base64"
)

var (
    //go:embed sammy-jetpack.png
    img []byte
)

type ResponseHeaders struct {
    ContentType string `json:"Content-Type"`
}

type Response struct {
    Body string          `json:"body"`
    Headers ResponseHeaders `json:"headers"`
}

func Main() Response {
    return Response{
        Body: b64.StdEncoding.EncodeToString(img),
        Headers: ResponseHeaders{
            ContentType: "image/png",
        },
    }
}

My example returns the image as is. Loading its URL in a web browser displays the image as the response body. To help me create the structs used for the response, including its headers, I consulted our docs on returning images from functions.

You would expand the example to add the processing for your use case.

Bobby · Answer

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Include and Find Files Included in Go Function

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