Go Network Programming Cheat Sheet

All the tables provided in the cheat sheets are also presented in tables below which are easy to copy and paste.

The Go Network Programming Cheat Sheet covers:

• Operators
• Variables
• Packages
• Comments
• Reserved Keywords
• Controls
• Arrays, Slices, & Ranges
• Functions
• TCP Socket Programming with Go
  • Creating a TCP client with Go
  • Creating a TCP Server with Go
  • Testing the TCP Client and Server with Go
• AWS Lambda Function Handler example with Go
• AWS Bucket List example with Go

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What’s included in this cheat sheet

The following categories and items have been included in the cheat sheet:

Operators

Variables

VarDecl = "var" ( VarSpec | "(" { VarSpec ";" } ")" )
VarSpec = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList )

var i int
var U, V, W float64
var k = 0
var x, y float32 = -1, -2
var (
i int
u, v, s = 2.0, 3.0, "bar"
)
var re, im = complexSqrt(-1)

Packages

// PackageClause = "package" PackageName
// PackageName = identifier

//ImportDecl = "import" ( ImportSpec | "(" { ImportSpec ";" } ")" )
//ImportSpec = [ "." | PackageName ] ImportPath
//ImportPath = string_lit

Comments

// Line comments

/* General comments - closed */

Reserved Keywords

Controls

if x > 0 {
return x
} else {
return -x
}

// Only `for`, no `while`, no `until`
for i := 1; i
}
for ; i
}
for i
}
for { // you can omit the condition ~ while (true)
}

switch tag {
default: s3()
case 0, 1, 2, 3: s1()
case 4, 5, 6, 7: s2()
}

Arrays, Slices, & Ranges

[32]byte
[2*N] struct { x, y int32 }
[1000]*float64
[3][5]int
[2][2][2]float64 // same as [2]([2]([2]float64))

make([]T, length, capacity)

// RangeClause = [ ExpressionList "=" | IdentifierList ":=" ] "range" Expression .

Functions

func function_name( [parameter list] ) [return_types]
{
Function body
}

TCP Socket Programming with Go

Creating a TCP client with Go

//create a file named tcpC.go
package main
import (
 "bufio"
 "fmt"
 "net"
 "os"
 "strings"
)
func main() {
 arguments := os.Args
 if len(arguments) == 1 {
 fmt.Println("Please provide host:port.")
 return
 }
 CONNECT := arguments[1]
 c, err := net.Dial("tcp", CONNECT)
 if err != nil {
 fmt.Println(err)
 return
}
 for {
 reader := bufio.NewReader(os.Stdin)
 fmt.Print(">> ")
 text, _ := reader.ReadString('n')
 fmt.Fprintf(c, text+"n")
 message, _ := bufio.NewReader(c).ReadString('n')
 fmt.Print("->: " + message)
 if strings.TrimSpace(string(text)) == "STOP" {
 fmt.Println("TCP client exiting...")
 return
 }
 }
}

Creating a TCP Server with Go

//create a file named tcpS.go
package main
import (
 "bufio"
 "fmt"
 "net"
 "os"
 "strings"
 "time"
)
func main() {
 arguments := os.Args
 if len(arguments) == 1 {
 fmt.Println("Please provide port number")
 return
 }
 PORT := ":" + arguments[1]
 l, err := net.Listen("tcp", PORT)
 if err != nil {
 fmt.Println(err)
 return
 }
 defer l.Close()
 c, err := l.Accept()
 if err != nil {
 fmt.Println(err)
 return
 }
 for {
 netData, err := bufio.NewReader(c).ReadString('n')
 if err != nil {
 fmt.Println(err)
 return
 }
 if strings.TrimSpace(string(netData)) == "STOP" {
 fmt.Println("Exiting TCP server!")
 return
 }
 fmt.Print("-> ", string(netData))
 t := time.Now()
 myTime := t.Format(time.RFC3339) + "n"
 c.Write([]byte(myTime))
 }
}

Testing the TCP Client and Server with Go

//Run your TCP server. From the directory containing the tcpS.go file, run the following command:
go run tcpS.go 1234
//The server will listen on port number 1234. You will not see any output as a result of this command.
//Open a second shell session to execute the TCP client and to interact with the TCP server. Run the following command:
go run tcpC.go 127.0.0.1:1234
//Note: If the TCP server is not running on the expected TCP port, you will get the following error message from tcpC.go:
dial tcp [::1]:1234: connect: connection refused
//You will see a >> prompt waiting for you to enter some text. Type in Hello! to receive a response from the TCP server:
Hello!
//You should see a similar output:
>> Hello!
->: 2019-05-23T19:43:21+03:00
//Send the STOP command to exit the TCP client and server:
STOP
//You should see a similar output in the client:
>> STOP
->: TCP client exiting...
//The output on the TCP server side will resemble the following:
-> Hello!
Exiting TCP server!

AWS Lambda Function Handler example with Go

package main
import (
 "fmt"
 "github.com/aws/aws-lambda-go/lambda"
)
type MyEvent struct {
 Name string 'json:"What is your name?"'
 Age int 'json:"How old are you?"'
}
type MyResponse struct {
 Message string 'json:"Answer:"'
}
func HandleLambdaEvent(event MyEvent) (MyResponse, error) {
 return MyResponse{Message: fmt.Sprintf("%s is %d years old!", event.Name,event.Age)}, nil
}
func main() {
 lambda.Start(HandleLambdaEvent)
}

AWS Bucket List example with Go

package main
import (
 "fmt"
 "github.com/aws/aws-sdk-go/aws"
 "github.com/aws/aws-sdk-go/aws/session"
 "github.com/aws/aws-sdk-go/service/s3"
)
func main() {
 s3svc := s3.New(session.New())
 result, err := s3svc.ListBuckets(&s3.ListBucketsInput{})
 if err != nil {
 fmt.Println("Buckets list failed", err)
 return
 }
 fmt.Println("Buckets:")
 for _, bucket := range result.Buckets {
 fmt.Printf("%s : %sn", aws.StringValue(bucket.Name), bucket.CreationDate)
 }
}