Snippets

Pick a random element in an array or slice in Go (Golang)
2023-01-01
Using the ‘math/rand’ package of golang to generate a pseudo-random number between [x,n). The bracket at the end means that n is exclusive and x could be any number 0 or greater. The package contains a function Intn which can be utilized to pick a random element in an array or slice of int or string. This example also uses the time package to seed the generator. Otherwise the it would be seeded with a 1 and the generated numbers wouldn’t be random.

A quick HTTP file server example in Go

2022-11-04

Basic example to serve directory.

package main

import (
    "flag"
    "fmt"
    "log"
    "net/http"
)

func main() {
    // Simple static webserver:
    pathPtr := flag.String("d", ".", "Directory path to serve")
    portPtr := flag.String("p", "8080", "Port to listen on")
    interfacePtr := flag.String("i", "", "Interface to listen on (default all)")
    flag.Parse()
    log.Printf("Serving %s on %s:%s", *pathPtr, *interfacePtr, *portPtr)
    err := http.ListenAndServe(fmt.Sprintf("%s:%s", *interfacePtr, *portPtr), http.FileServer(http.Dir(*pathPtr)))
    if err != nil {
        log.Fatal(err)
    }
}

Example with ability to set custom headers

package main

import (
    "flag"
    "fmt"
    "log"
    "net/http"
)

func main() {
    // Simple static webserver:
    pathPtr := flag.String("d", ".", "Directory path to serve")
    portPtr := flag.String("p", "8080", "Port to listen on")
    interfacePtr := flag.String("i", "", "Interface to listen on (default all)")
    flag.Parse()
    log.Printf("Serving %s on %s:%s", *pathPtr, *interfacePtr, *portPtr)
    fs := http.FileServer(http.Dir(*pathPtr))
    err := http.ListenAndServe(fmt.Sprintf("%s:%s", *interfacePtr, *portPtr), customHeaders(fs))
    if err != nil {
        log.Fatal(err)
    }
}

func customHeaders(fs http.Handler) http.HandlerFunc {
    // found at https://stackoverflow.com/a/65905091
    return func(w http.ResponseWriter, r *http.Request) {
        // add headers etc here
        // return if you do not want the FileServer handle a specific request
        w.Header().Set("Cache-Control", "no-cache")
        w.Header().Set("x-server", "hello, world!")
        fs.ServeHTTP(w, r)
    }
}

Example of adding CORS headers Flask

2022-11-04

An example of adding CORS headers to a Flask app without using Flask-CORS.

from flask import Flask, request, jsonify, make_response
from werkzeug.datastructures import Headers

app = Flask(__name__)

@app.route('/', methods=['OPTIONS', 'GET', 'POST'])
def index():
    # output all request headers to terminal
    print(request.headers)
    
    if request.method == 'POST':
        # handle json post data here...
        print(request.get_json())

    headers = Headers()
    headers.add('Access-Control-Allow-Origin', '*')
    headers.add('Access-Control-Allow-Methods', 'OPTIONS', 'GET', 'POST')
    headers.add('Access-Control-Allow-Headers', 'Content-Type')
    headers.add('Access-Control-Max-Age', '300')
    
    resp = make_response(
                jsonify(
                    {'msg':'nailed it!'}
                )
            )
    
    resp.headers = headers
    return resp

if __name__ == '__main__':
    app.run(debug=True)

Pick a random element in an array or slice in Go (Golang)

A quick HTTP file server example in Go

Example of adding CORS headers Flask