GO CONTEXT

Official doc

The go programming language standard library ships with a package called context. This package is basically used for maintaining a, uhm, context in a time-bound lifecycle. A time-bound lifecycle, like, for example, a request/response cycle.

context.Context can serve as a key/value store over the course of a request lifetime on a server.

Here’s a contrived example.

import (
  "context",
  "fmt"
)

func enrichContext(ctx context.Context) context.Context {
  // set a key/value
  ctx.WithValue(ctx, "request-id", "12345")
  return ctx
}

func logRequestId(ctx context.Context) {
  // access value
  rId := ctx.Value("request-id")
  fmt.Printf("Request ID: %s", rId)
}

func main() {
  // initalize a contex
  ctx := context.Background()
  ctx = enrichContext(ctx)
  logRequestId(ctx)
}

This key/value feature is just the icing on top of the cake. The real use case of context is for managing timeouts/deadlines, timeboxing request lifecycles, etc.