How do I get GoLang's http.HandleFunc() to work without error?

I am trying to create a GoLang http.HandleFunc() that will listen for post requests and parse a json file. The Handler seems to fail as it starts and returns an error:

> 2017/01/24 13:35:08 listen tcp :8080: bind: Only one usage of each
> socket address (protocol/network address/port) is normally permitted.

I am assuming that it is throwing a fatal error.

Below is my function:

 http.HandleFunc("/", func(w http.ResponseWriter, request *http.Request) {
		
		//debug
		fmt.Fprintf(w, "Hello, %q", html.EscapeString(request.URL.Path))
		
        var m Message

        if request.Body == nil {
            http.Error(w, "Please send a request body", 400)	            
            return
        }
        
        err := json.NewDecoder(request.Body).Decode(&m)
        if err != nil {
            http.Error(w, err.Error(), 400)
            return
        }
 })
 log.Fatal(http.ListenAndServe(":8080", nil))

How can I get this Handler to work and not get the error?

I've remedied several of the problems with your code and made best guesses around missing information. Here is sample working code that will accept a message that has "name" and "text" fields:

package main

import (
  "encoding/json"
  "fmt"
  "html"
  "log"
  "net/http"
)

type Message struct {
  Name string `json:"name"`
  Text string `json:"text"`
}
    
func main() {
  http.HandleFunc("/", func(w http.ResponseWriter, request *http.Request) {
    fmt.Fprintf(w, "Hello, %q", html.EscapeString(request.URL.Path))

    var m Message

    if request.Body == nil {
      http.Error(w, "Please send a request body", 400)
      return
    }

    err := json.NewDecoder(request.Body).Decode(&m)
    if err != nil {
      http.Error(w, err.Error(), 400)
      return
    }

    log.Println(m)
  })
   
  log.Fatal(http.ListenAndServe(":8080", nil))
}