qbig

There are three easy to make mistakes in go. I present them here in the way they are often found in the wild, not in the way that is easiest to understand.

All three of these mistakes have been made in Kubernetes code, getting past code review at least once each that I know of.

1. Loop variables are scoped outside the loop.

What do these lines do? Make predictions and then scroll down.

func print(pi *int) { fmt.Println(*pi) }

qbig

Keybase proof

I hereby claim:

• I am qbig on github.
• I am qbig (https://keybase.io/qbig) on keybase.
• I have a public key ASAcbDSXyirF0x6Qbwpa9_2GnsP-zSlexmRBXs_HTzRoTwo

To claim this, I am signing this object:

qbig

package cache_test

import (
	"fmt"
	"time"

	"github.com/go-redis/redis"
	"github.com/vmihailenco/msgpack"

	"github.com/go-redis/cache"

qbig

package main

import "fmt"
import flag "github.com/spf13/pflag"

func main() {
	var f1 *int = flag.Int("f1", 1, "help message for flagname")
	var f2 *int = flag.Int("f2", 2, "help message for flagname")
	flag.Parse()
	fmt.Println(*f1)

qbig

// slower but easier & loosely typed interface
sugar := zap.NewExample().Sugar()
defer sugar.Sync()
sugar.Infow("failed to fetch URL",
  "url", "http://example.com",
  "attempt", 3,
  "backoff", time.Second,
)
sugar.Infof("failed to fetch URL: %s", "http://example.com")

qbig

package main

import (
	"context"
	"flag"
	"fmt"
	"html/template"
	"log"
	"net/http"
	"os"

qbig

// A minimal example of how to include Prometheus instrumentation.
package main

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

	"github.com/prometheus/client_golang/prometheus/promhttp"
)

qbig

// A simple example exposing fictional RPC latencies with different types of
// random distributions (uniform, normal, and exponential) as Prometheus
// metrics.
package main

import (
	"flag"
	"log"
	"math"

qbig

import "github.com/grpc-ecosystem/go-grpc-middleware"

myServer := grpc.NewServer(
    grpc.StreamInterceptor(grpc_middleware.ChainStreamServer(
        grpc_ctxtags.StreamServerInterceptor(),
        grpc_opentracing.StreamServerInterceptor(),
        grpc_prometheus.StreamServerInterceptor,
        grpc_zap.StreamServerInterceptor(zapLogger),
        grpc_auth.StreamServerInterceptor(myAuthFunction),
        grpc_recovery.StreamServerInterceptor(),

qbig

sql.DB is a abstraction of DB relation operations. It is not a connection Thus, to check if a connection is open, we need to db.Ping()

db, err := sql.Open("mysql", "user:password@/dbname")
if err != nil {
    panic(err.Error()) // Just for example purpose. You should use proper error handling instead of panic
}
defer db.Close()

// Open doesn't open a connection. Validate DSN data: