What data transfer protocols have you used to interact with the application’s client side?

The most commonly used data transfer protocols for interacting with the client part of a Go application are:

• HTTP/HTTPS — the most widespread protocol for web applications, allowing data exchange in JSON, XML, and other formats.
• WebSocket — a protocol for bidirectional real-time communication, useful for chats, games, and other interactive applications.
• gRPC — a modern protocol based on HTTP/2 with support for binary serialization, efficient for microservices.

Example of a simple HTTP server in Go:

package main

import (
    "net/http"
    "fmt"
)

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, client!")
}

func main() {
    http.HandleFunc("/", handler)
    http.ListenAndServe(":8080", nil)
}

Thus, the choice of protocol depends on requirements for speed, reliability, and data type.