content-length-client.go

package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"strings"
)

type StrBuf struct {
	data []byte
	off  int
}

func (buf *StrBuf) Read(p []byte) (int, error) {
	if buf.off >= len(buf.data) {
		return 0, io.EOF
	}

	n := copy(p, buf.data[buf.off:])
	buf.off += n

	if buf.off > len(buf.data) {
		return 0, fmt.Errorf("over-read?  len(buf.data) = %d, but buf.off = %d", len(buf.data), buf.off)
	}

	return n, nil
}

func main() {
	body := `{"foo":5}`

	client := http.Client{}

	urlStr := "http://localhost:9999/foo"
	var rdr io.Reader

	// comment out one of the following lines
	rdr = &StrBuf{data: []byte(body)}
	rdr = strings.NewReader(body)

	req, err := http.NewRequest("POST", urlStr, rdr)
	if err != nil {
		log.Fatalf("failed to make request: %s", err)
	}

	req.Header.Set("Content-Type", "application/json")

	rsp, err := client.Do(req)
	if err != nil {
		log.Fatalf("failed to do post: %s", err)
	}

	log.Printf("done!  status = %s", rsp.Status)
}