Can't run the go routines while building chat app with golang - go

Question

I'm trying to build a chat app with golang. However, I've encountered a problem that if I wrap the code of the for loop into a Sender() function and using goroutines, the client will shut down immediately. But if I put it in the main function, it can run correctly.
Here is the client code.
package main
import (
"fmt"
"net"
"os"
"os/signal"
"syscall"
)
const (
SERVER_HOST = "localhost"
SERVER_PORT = "9988"
SERVER_TYPE = "tcp"
)
var connection net.Conn
var err error
func main() {
SetupCloseHandler()
//establish connection
connection, err = net.Dial(SERVER_TYPE, SERVER_HOST+":"+SERVER_PORT)
if err != nil {
panic(err)
}
//receive some data
go Receiver()
// go Sender()
for {
var input string
fmt.Print("Enter text: ")
fmt.Scan(&input)
_, err = connection.Write([]byte(input))
if err != nil {
panic(err)
}
}
}
// func Sender() {
// for {
// var input string
// fmt.Print("Enter text: ")
// fmt.Scan(&input)
// _, err = connection.Write([]byte(input))
// if err != nil {
// panic(err)
// }
// }
// }
func Receiver() {
for {
buffer := make([]byte, 1024)
mLen, err := connection.Read(buffer)
if err != nil {
panic(err)
}
fmt.Println("Received: ", string(buffer[:mLen]))
}
}
func SetupCloseHandler() {
c := make(chan os.Signal, 2)
signal.Notify(c, os.Interrupt, syscall.SIGTERM)
go func() {
<-c
fmt.Println("\r- Ctrl+C pressed in Terminal")
os.Exit(0)
}()
}
Here is the server code.
package main
import (
"fmt"
"net"
"os"
"github.com/google/uuid"
)
const (
SERVER_HOST = "localhost"
SERVER_PORT = "9988"
SERVER_TYPE = "tcp"
)
var clientMap = make(map[string]net.Conn)
func main() {
fmt.Println("Server Running...")
server, err := net.Listen(SERVER_TYPE, SERVER_HOST+":"+SERVER_PORT)
if err != nil {
fmt.Println("Error listening:", err.Error())
os.Exit(1)
}
defer server.Close()
fmt.Println("Listening on " + SERVER_HOST + ":" + SERVER_PORT)
fmt.Println("Waiting for client...")
for {
connection, err := server.Accept()
id := uuid.New().String()
clientMap[id] = connection
if err != nil {
fmt.Println("Error accepting: ", err.Error())
os.Exit(1)
}
fmt.Printf("client %s connected\n", id)
go processClient(connection, id)
}
}
func processClient(connection net.Conn, id string) {
defer connection.Close()
for {
buffer := make([]byte, 1024)
mLen, err := connection.Read(buffer)
if err != nil {
fmt.Println("Error reading:", err.Error())
delete(clientMap, id)
connection.Close()
return
}
fmt.Println("Received: ", string(buffer[:mLen]))
for k, c := range clientMap {
if k != id {
c.Write(buffer[:mLen])
}
}
}
}