entr and go run not playing nice

I'm doing some light web development in go, and running into a problem with entr. I'm editing .go files in a directory while having

ls *.go | entr -r go run *.go

running in a separate terminal window.

I can see it re-starting my program every time I save a file, because some format statements get printed out to the terminal every time I do so. However, whenever I navigate to localhost:8080, I see the handler content that was present when I started entr (rather than the content in the most recent change). If I Ctrl+C, then restart entr, I see the latest changes.

Any idea what I'm doing wrong?

Here's the minimal example:

// test.go
package main
import (
	"fmt"
	"net/http"
)
func handler (w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Hello there! I love %s!", r.URL.Path[1:])
}
func main() {
	fmt.Println("Starting up...")
	http.HandleFunc("/", handler)
	http.ListenAndServe(":8080", nil)
}

Now, if I run ls test.go | entr -r go run test.go, I see Starting up... printed to the terminal, and I can go to localhost:8080/tests to see a page that says "Hello there! I love tests!". If I change the handler function so that it reads

func handler (w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "I guess %s are ok...", r.URL.Path[1:])
}

I see the Starting up... message printed in terminal again, but going to localhost:8080/tests still gives me the page showing "Hello there! I love tests!" (even in incognito mode). If I then kill the entr process and restart it, I can go to localhost:8080/tests to see I guess tests are ok... as expected.

Edit:

Getting the error out of ListenAndServe confirms that this has to do with a dangling socket.

...
   err := http.ListenAndServe(":8080", nil)
   fmt.Printf("ListenAndServe ERR: %s\n", err)
...

shows the extra line

listen tcp :8080: bind: address already in use

in terminal. A quick search tells me that there isn't an easy way to stop a listener started with ListenAndServe. Is there a simpler approach than this?

The ls command only lists the go files in your current directory. The command should be like this to listen to go files in all subfolders in the project.

find . | grep '\.go' | entr -r go run .

The problem:
go run will start the server in a separate process which won't be killed.

A solution:
Use a little script which kills and starts the server

#!/bin/sh
pkill "$1"
go run "$1.go"

and use this for entr.

In linux there are two process created. First is the go run main.go and the second is the /tmp/go-build/<random number>b001/exe/main. The second one needs to be killed to terminate the program not the first...