golang Resource interpreted as Stylesheet but transferred with MIME type text/plain

I have a problem in developing my webpage using golang. server file (main.go):

package main

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

type MyHandler struct {
}

func (this *MyHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    path := r.URL.Path[1:]
    log.Println(path)
    data, err := ioutil.ReadFile(string(path))

    if err == nil {
        var contentType string

        if strings.HasSuffix(path, ".css") {
            contentType = "text/css"
        } else if strings.HasSuffix(path, ".html") {
            contentType = "text/html"
        } else if strings.HasSuffix(path, ".js") {
            contentType = "application/javascript"
        } else if strings.HasSuffix(path, ".png") {
            contentType = "image/png"
        } else if strings.HasSuffix(path, ".svg") {
            contentType = "image/svg+xml"
        } else {
            contentType = "text/plain"
        }

        w.Header().Add("Content Type", contentType)
        w.Write(data)
    } else {
        w.WriteHeader(404)
        w.Write([]byte("404 Mi amigo - " + http.StatusText(404)))
    }
}

func main() {
    http.Handle("/", new(MyHandler))
    http.ListenAndServe(":8080", nil)
}

But when i type http://localhost:8080/templates/home.html this what i see see screenshot Why my page is not loaded right?? where is my css?? whyy is the error "Resource interpreted as Stylesheet but transferred with MIME type text/plain:" appears while i have my content Type in main.go handled??

Your basic problem is very simple: You need Content-Type instead of Content Type.

However, there is a better way to match MIME types to file extensions in Go, specifically the mime standard library package. I would strongly suggest that you use it.