Go

Snippets

Reusable snippets.

Interface assertion

Go’s interfaces are implicit, but this can be frustrating when trying to debug missing or incorrect receiver function implementations as you will only be warned at the call-site of the interface usage.

var _ InterfaceType = (*ImplementationType)(nil)

The best part is, this doesn’t actually assign or construct anything, so there’s no run-time overhead.

A full example:

type DB interface {
  GetUser(id uuid.UUID) error
}

type PostgresDB struct {
  conn *pgx.Conn
}

func (db *PostgresDb) GetUser(id uuid.UUID) error  {
  // do stuff
}

var _ DB = (*PostgresDB)(nil)

Reading all input from stdin

package main

import (
  "bufio"
  "fmt"
  "os"
)

func main() {
  scanner := bufio.NewScanner(os.Stdin)
  for scanner.Scan() {
    fmt.Println(scanner.Text())
  }
}

Usage:

cat <<EOF | go run main.go --
apple
banana
waffle
EOF