Test coverage in API - unit-testing

Question

I'm learning tests in Go and I have been trying to measure test coverage in an API that I created:
main.go
package main
import (
"encoding/json"
"log"
"net/http"
)
func main() {
http.HandleFunc("/", SimpleGet)
log.Print("Listen port 8080")
log.Fatal(http.ListenAndServe(":8080", nil))
}
// SimpleGet return Hello World
func SimpleGet(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != "/" {
http.NotFound(w, r)
}
w.Header().Set("Content-Type", "application/json")
data := "Hello World"
switch r.Method {
case http.MethodGet:
json.NewEncoder(w).Encode(data)
default:
http.Error(w, "Invalid request method", 405)
}
}
And the test:
main_test.go
package main
import (
"net/http"
"net/http/httptest"
"strings"
"testing"
)
func TestSimpleGet(t *testing.T) {
req, err := http.NewRequest("GET", "/", nil)
if err != nil {
t.Fatal(err)
}
w := httptest.NewRecorder()
SimpleGet(w, req)
resp := w.Result()
if resp.Header.Get("Content-Type") != "application/json" {
t.Errorf("handler returned wrong header content-type: got %v want %v",
resp.Header.Get("Content-Type"),
"application/json")
}
if status := w.Code; status != http.StatusOK {
t.Errorf("handler returned wrong status code: got %v want %v", status, http.StatusOK)
}
expected := `"Hello World"`
if strings.TrimSuffix(w.Body.String(), "\n") != expected {
t.Errorf("handler returned unexpected body: got %v want %v", w.Body.String(), expected)
}
}
When I run go test it is fine, the test has passed. But when I try to get the test coverage, I got this HTML:
I would like to understand what is happened here because it has not covered anything. Does anyone know to explain?

Answer 1

I have found my error:
I was trying to run the test coverage with these commands:
$ go test -run=Coverage -coverprofile=c.out
$ go tool cover -html=c.out
But the correct commands are:
$ go test -coverprofile=c.out
$ go tool cover -html=c.out
Result:
OBS: I wrote one more test to cover all switch statements. Thanks for all, and I'm sorry if I disturbed someone.