Golang HTTP multipart streaming

client.go

package main

import (
	"io"
	"mime/multipart"
	"net/http"
	"net/url"
	"os"
	"fmt"
)

const boundary = "MachliJalKiRaniHaiJeevanUskaPaaniHai"

func main() {
	tr := http.DefaultTransport

	client := &http.Client{
		Transport: tr,
		Timeout:   0,
	}
	
	fmt.Println("Set up pipe")
	pR, pW := io.Pipe()

	go func() {
		// Set up multipart body for reading
		multipartW := multipart.NewWriter(pW)
		fmt.Println("Set up multipart writer")
		multipartW.SetBoundary(boundary)
		fmt.Println("Set up boundary")	
		partW, err0 := multipartW.CreateFormFile("fakefield", "fakefilename")
		fmt.Println("Set up part writer")	
		if err0 != nil {
			panic("Something is amiss creating a part")
		}

		connector := io.TeeReader(os.Stdin, partW)
		buf := make([]byte, 256)
		for {
			/* stdin -> connector -> partW -> multipartW -> pW -> pR */
			_, err := connector.Read(buf) 
			if err == io.EOF {
				break
			}
			if err != nil {
				fmt.Printf("The error reading from connector: %v", err)
			}
		}
		
	}()

	// Send http request chunk encoding the multipart message
	req := &http.Request{
		Method: "POST",
		URL: &url.URL{
			Scheme: "http",
			Host:   "localhost:9094",
			Path:   "/",
		},
		ProtoMajor: 1,
		ProtoMinor: 1,
		ContentLength: -1,
		Body: pR, 
	}
	fmt.Printf("Doing request\n")
	_, err := client.Do(req)
	fmt.Printf("Done request. Err: %v\n", err)
}

server.go

package main

import (
	"mime/multipart"
	"net/http"
	"net"
	"fmt"
	"io"
)

const boundary = "MachliJalKiRaniHaiJeevanUskaPaaniHai"

func handle(w http.ResponseWriter, req *http.Request) {
	partReader := multipart.NewReader(req.Body, boundary)
	buf := make([]byte, 256)
	for {
		part, err := partReader.NextPart()
		if err == io.EOF {
			break
		}
		var n int
		for {
			n, err = part.Read(buf)
			if err == io.EOF {
				break
			}
			fmt.Printf(string(buf[:n]))
		}
		fmt.Printf(string(buf[:n]))
	}
}

func main() {
	/* Net listener */
	n := "tcp"
	addr := "127.0.0.1:9094"
	l, err := net.Listen(n, addr)
	if err != nil {
		panic("AAAAH")
	}

	/* HTTP server */
	server := http.Server{
		Handler: http.HandlerFunc(handle),
	}
	server.Serve(l)
}

Thank you for this! It worked well for me after I added the suggestions from @robtimus

diff --git a/client.go b/client.go
index a9fb70b..642cba8 100644
--- a/client.go
+++ b/client.go
@@ -1,12 +1,12 @@
 package main

 import (
+       "fmt"
        "io"
        "mime/multipart"
        "net/http"
        "net/url"
        "os"
-       "fmt"
 )

 const boundary = "MachliJalKiRaniHaiJeevanUskaPaaniHai"
@@ -31,7 +31,7 @@ func main() {
                partW, err0 := multipartW.CreateFormFile("fakefield", "fakefilename")
                fmt.Println("Set up part writer")
                if err0 != nil {
-                       panic("Something is amiss creating a part")
+                       pW.CloseWithError(err0)
                }

                connector := io.TeeReader(os.Stdin, partW)
@@ -40,13 +40,14 @@ func main() {
                        /* stdin -> connector -> partW -> multipartW -> pW -> pR */
                        _, err := connector.Read(buf)
                        if err == io.EOF {
+                               multipartW.Close()
+                               pW.Close()
                                break
                        }
                        if err != nil {
                                fmt.Printf("The error reading from connector: %v", err)
                        }
                }
-
        }()

        // Send http request chunk encoding the multipart message

@patientplatypus You need to pipe data into it, akin to

cat file.txt | ./client