Developing a UUID generation API using ServeMux

A UUID is a unique identifier for a resource or a transaction. UUIDs are widely used for identifying an HTTP request. Let us develop an API for generating a UUID. Please follow these steps:

1. Create the program file as follows:

touch -p $GOPATH/src/github.com/git-user/chapter2/uuidGenerator/main.go

2. Any Go struct with a few dedicated HTTP methods is qualified to be a ServeMux. For example, we can create a custom UUID struct and implement the ServeHTTP function in order to make it a ServeMux object. Following is the implementation for the uuidGenerator.go module:

import (
  "crypto/rand"
  "fmt"
)

// UUID is a custom multiplexer
type UUID struct {
}

func (p *UUID) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  if r.URL.Path == "/" {
    giveRandomUUID(w, r)
    return
  }
  http.NotFound(w, r)
  return
}

func giveRandomUUID(w http.ResponseWriter, r *http.Request) {
 c := 10
  b := make([]byte, c)
  _, err := rand.Read(b)
  if err != nil {
    panic(err)
  }
  fmt.Fprintf(w, fmt.Sprintf("%x", b))
}

It consists of the UUID struct that acts as a ServeMux object. We can access the URL path in the handler function and use that information to manually route the requests to different response generators.

giveRandomUUID is a response generator function that sets a random UUID string to response. Go's crypto package has a Read function that fills random characters into a byte array.

3. Now add a main function to the module using the ServeMux object. We should pass our ServeMux to the  http.ListenAndServe function to get our content served. We are serving our content on port 8000:

package main

import (
  "net/http"
)

func main() {
  mux := &UUID{}
  http.ListenAndServe(":8000", mux)
}

We use UUID as a multiplexer in the ListenAndServe function, which starts an HTTP server. The server executes the ServeHTTP method that is defined preceding on the mux object.

4. Run the following command from your shell/Terminal:

go run $GOPATH/src/github.com/git-user/chapter2/uuidGenerator/main.go

5. We can make a curl request like this to make a request to the web server that is listening on port 8000:

curl -X GET http://localhost:8000/

The response that is returned will be a random string:

544f5519592ac25bb2c0

Until now, we have worked with a single handler. Let us see how we can add multiple handlers to route to different function handlers using ServeMux.