qbig

Deferring inside a loop. A long-lived function with a query inside a loop, and defer rows.Close() inside the loop, will cause both memory and connection usage to grow without bounds.

Opening many db objects. Make a global sql.DB, and don’t open a new one for, say, every incoming HTTP request your API server should respond to. Otherwise you’ll be opening and closing lots of TCP connections to the database. It’s a lot of latency, load, and TCP connections in TIME_WAIT status.

qbig

Channel Axioms

A send to a nil channel blocks forever A receive from a nil channel blocks forever

A send to a closed channel panics A receive from a closed channel returns the zero value immediately

Check if a channel is closed

qbig

Pipeline

func gen(nums ...int) <-chan int {
    out := make(chan int)
    go func() {
        for _, n := range nums {
            out <- n
        }
        close(out)
    }()

qbig

Server

flag.Parse()
lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
if err != nil {
        log.Fatalf("failed to listen: %v", err)
}
grpcServer := grpc.NewServer()
pb.RegisterRouteGuideServer(grpcServer, &routeGuideServer{})
// ... // determine whether to use TLS

qbig

func server(workChan <-chan *Work) {
    for work := range workChan {
        go safelyDo(work)
    }
}

func safelyDo(work *Work) {
    defer func() {
 if err := recover(); err != nil {

qbig

The io.Reader and io.Writer interfaces

type Reader interface {
        Read(p []byte) (n int, err error)
}

type Writer interface {
        Write(p []byte) (n int, err error)
}

qbig

Working with buffer

        package bytestrings

        import (
                "bytes"
                "io"
                "io/ioutil"
        )

qbig

Working with dir

 package filedirs

        import (
                "errors"
                "io"
                "os"
        )

qbig

Reading CSV

  package csvformat

        import (
                "bytes"
                "encoding/csv"
                "fmt"
                "io"
                "strconv"

qbig

Working with template

 package templates

        import (
                "os"
                "strings"
                "text/template"
        )