remote debug golang dlv wait for a client to connect before continuing the code (visual studio code client)

Question

I like to be able do very simple thing wait for the client to connect to dlv debugger before continue the code without success . i have simple go server :

package main

import (
    "fmt"
    "net/http"
)

func hello(w http.ResponseWriter, req *http.Request) {

    fmt.Fprintf(w, "hello\n")
}

func headers(w http.ResponseWriter, req *http.Request) {

    for name, headers := range req.Header {
        for _, h := range headers {
            fmt.Fprintf(w, "%v: %v\n", name, h)
        }
    }
}

func main() {
    fmt.Println("server started now!")
    http.HandleFunc("/hello", hello)
    http.HandleFunc("/headers", headers)

    http.ListenAndServe(":8090", nil)
}

i start the server on the linux mechine like this:

vagrant@vagrant:~/go_dev/very_simple_server_dir$ dlv debug /home/vagrant/go_dev/very_simple_server_dir/very_simple_server.go --headless --listen=:3000  --log
API server listening at: [::]:3000
2022-10-31T06:18:47Z warning layer=rpc Listening for remote connections (connections are not authenticated nor encrypted)
2022-10-31T06:18:47Z info layer=debugger launching process with args: [/home/vagrant/go_dev/very_simple_server_dir/__debug_bin]
2022-10-31T06:18:47Z warning layer=debugger can't find build-id note on binary

in visual studio code the launch.json looks like this :

"version": "0.2.0",
    "configurations": [
        {
            "name": "Connect to server",
            "type": "go",
            "request": "attach",
            "mode": "remote",
            "remotePath": "/home/vagrant/go_dev/very_simple_server_dir/",
            "cwd" : "${workspaceFolder}",
            "port": 3000,
            "host": "127.0.0.1",
            "trace": "verbose",
            "asRoot": true,
        }
    ]

it connectes just fine to the remote server the problem is that i like the dlv debug server wait to the client to connect before it execute the go code . i want to be able to set break point in func main() second line

how can i do that ?

Answer 1

The second line in your main.go does no more than register your handler function (hello in this case). This happens before your app is started with ListenAndServe().

I assume you want to debug your app after it is started. You may want to set a breakpoint at the first (and the only) line of your hello function.