GitLab API v4 POST /projects/:id/uploads

main.go

package main

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

func main() {
	url := "https://gitlab.com/api/v4/projects/18630472/uploads"
	fieldname := "file"
	filename := "hello.txt"
	file, err := os.Open(filename)
	if err != nil {
		log.Fatal(err)
	}

	body := &bytes.Buffer{}
	mw := multipart.NewWriter(body)
	fw, err := mw.CreateFormFile(fieldname, filename)
	if err != nil {
		log.Fatal(err)
	}

	_, err = io.Copy(fw, file)
	if err != nil {
		log.Fatal(err)
	}

	contentType := mw.FormDataContentType()

	if err := mw.Close(); err != nil {
		log.Fatal(err)
	}

	req, err := http.NewRequest(http.MethodPost, url, body)
	if err != nil {
		log.Fatal(err)
	}

	req.Header.Set("Content-Type", contentType)
	req.Header.Set("Authorization", "")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		log.Fatal(err)
	}

	b, err := io.ReadAll(resp.Body)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(string(b))
}