Shim is a thin layer between API Gateway integration requests via Lambda and the standard library http.Handler interface. It allows you to write plain ol' Go and run it on Lambda with minimal modifications. Bring your own router!

Shim uses dep to manage its dependencies. You can add shim to your dep project by running:

dep ensure -add github.com/iamatypeofwalrus/shim

The codebase is semantically versioned so feel free to update to pull the latest version with:

dep ensure -update github.com/iamatypeofwalrus/shim

You'll want to use the proxy pass integration with API Gateway to make sure your application receives every request sent to your API Gateway endpoint.

# Here we're using the SAM specification to define our function
#
# Note: You need both the Root AND the Greedy event in order to capture all
#       events sent to your web app.
YourFunction:
  Type: AWS::Serverless::Function
  Properties:
    Handler: main
    Runtime: go1.x
    Role: ...
    Events:
      ProxyApiRoot:
        Type: Api
        Properties:
          Path: /
          Method: ANY
      ProxyApiGreedy:
        Type: Api
        Properties:
          Path: /{proxy+}
          Method: ANY

package main

import (
  "fmt"
  "net/http"

  "github.com/aws/aws-lambda-go/lambda"

  "github.com/iamatypeofwalrus/shim"
)

func main() {
  // Create a router as normal. Any router that satisfies the http.Handler interface
  // is accepted!
  mux := http.NewServeMux()
  mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
    fmt.Fprint(w, "hello, world")
  })

  s := shim.New(mux)

  // Pass your router to shim and let Lambda handle the rest
  lambda.Start(s.Handle)
}

You can pull logs from various steps in the shim by passing the SetDebugLogger option. It accepts any logger that provides the Println and Printf functions a lá the standard library logger.

func main() {
  ...

  l := log.New(os.Stdout, "", log.LstdFlags)
  shim := shim.New(
    nil, // or your mux
    shim.SetDebugLogger(l)
  )

  ...
}