转到：http.Request中的read方法

I'm reading Go Web Programming by Sau Sheong Chang. Here is a sample code for reading data from a request body:

import (
    "fmt"
    "net/http"
)

func bodyfunc(w http.ResponseWriter, r *http.Request) {
    len := r.ContentLength
    body := make([]byte, len)
    r.Body.Read(body)
    fmt.Fprintln(w, string(body))
}

func main() {
    server := http.Server{
        Addr: "127.0.0.1:8080",
    }
    http.HandleFunc("/body", bodyfunc)
    server.ListenAndServe()
}

By definition, the Body field in the Request struct is actually an io.ReadCloser interface. My question is: The Read method in this interface is just declared but not implemented. Meanwhile the code works well. The implementation of the Read method must have been done somewhere. Where is it?

The implementation is in https://golang.org/src/net/http/transfer.go#L637. I used the delve debugger to find it.