How to see generated pdf on localhost webpage in Golang?

I am trying to see my generated pdf on http://localhost:3333/pdf.

I am trying to learn generating pdf using golang. Tying to make the changes in pdf and see live on localhost server ( http://localhost:3333/pdf ).
But I am clueless that how can I show pdf on localhost.

My Code::

package main
import (
"errors"
"fmt"
"io"
"net/http"
"os"
"github.com/krazybee/gofpdf"
)
type bufWriter struct {
buf []byte
}
func getRoot(w http.ResponseWriter, r *http.Request) {
fmt.Printf("got / request\n")
io.WriteString(w, "This is my website!\n")
}
func getHello(w http.ResponseWriter, r *http.Request) {
fmt.Printf("got /hello request\n")
io.WriteString(w, "Hello, HTTP!\n")
}
func generatePDF(w http.ResponseWriter, r *http.Request) {
pw := new(bufWriter)
pdf := gofpdf.New("P", "mm", "A4", "")
fontsize := 12.0
font := "Arial"
pdf.SetFont("Arial", "", 6)
pdf.AddPage()
pdf.SetMargins(5, 5, 5)
pdf.SetAutoPageBreak(true, 34)
pdf.SetFont(font, "B", fontsize)
pdf.MultiCell(0, 8, "TERMS OF LIVING", "", "C", false)
pdf.MultiCell(0, 8, "Terms", "", "C", false)
// Show the pdf on localhost web page.
err = pdf.OutputAndClose(pw)
if err != nil {
fmt.Println(err)
return
}
fmt.Println("PDF served successfully")
}
func main() {
http.HandleFunc("/", getRoot)
http.HandleFunc("/hello", getHello)
http.HandleFunc("/pdf", generatePDF)
err := http.ListenAndServe(":3333", nil)
if errors.Is(err, http.ErrServerClosed) {
fmt.Printf("server closed\n")
} else if err != nil {
fmt.Printf("error starting server: %s\n", err)
os.Exit(1)
}
}

This is what I have tried.
But from the comment // Show the pdf on the localhost web page. I don't know how to proceed further after that.

Can someone help me how can I do that? How can I see the generated pdf on a localhost web page?

By default http package serves the page with Content-type: text/html header. You have to specify the needed header by yourself before writing the page content:

w.Header().Set("Content-Type", "application/pdf")

However, the sample code you provided does not work, because a mess with io streams. Here is what you need to change:

func generatePDF(w http.ResponseWriter, r *http.Request) {
var b bytes.Buffer
pw := io.Writer(&b)
pr := io.Reader(&b)
...
err := pdf.Output(pw)
...
w.Header().Set("Content-Type", "application/pdf")
resPDF, _ := ioutil.ReadAll(pr)
w.Write(resPDF)
fmt.Println("PDF served successfully")
}

I suggest you to have some practice with io library.

Here is the full code that works for me:

package main
import (
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"github.com/krazybee/gofpdf"
)
func getRoot(w http.ResponseWriter, r *http.Request) {
fmt.Printf("got / request\n")
io.WriteString(w, "This is my website!\n")
}
func getHello(w http.ResponseWriter, r *http.Request) {
fmt.Printf("got /hello request\n")
io.WriteString(w, "Hello, HTTP!\n")
}
func generatePDF(w http.ResponseWriter, r *http.Request) {
var b bytes.Buffer
pw := io.Writer(&b)
pr := io.Reader(&b)
pdf := gofpdf.New("P", "mm", "A4", "")
fontsize := 12.0
font := "Arial"
pdf.SetFont("Arial", "", 6)
pdf.AddPage()
pdf.SetMargins(5, 5, 5)
pdf.SetAutoPageBreak(true, 34)
pdf.SetFont(font, "B", fontsize)
pdf.MultiCell(0, 8, "TERMS OF LIVING", "", "C", false)
pdf.MultiCell(0, 8, "Terms", "", "C", false)
// Show the pdf on localhost web page.
err := pdf.Output(pw)
if err != nil {
fmt.Println(err)
return
}
w.Header().Set("Content-Type", "application/pdf")
resPDF, _ := ioutil.ReadAll(pr)
w.Write(resPDF)
fmt.Println("PDF served successfully")
}
func main() {
http.HandleFunc("/", getRoot)
http.HandleFunc("/hello", getHello)
http.HandleFunc("/pdf", generatePDF)
err := http.ListenAndServe(":3333", nil)
if errors.Is(err, http.ErrServerClosed) {
fmt.Printf("server closed\n")
} else if err != nil {
fmt.Printf("error starting server: %s\n", err)
os.Exit(1)
}
}