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

Arithmetic operators
+ sum integers, floats, complex values, strings
difference integers, floats, complex values
* product integers, floats, complex values
/ quotient integers, floats, complex values
% remainder integers
& bitwise AND integers
| bitwise OR integers
^ bitwise XOR integers
&^ bit clear (AND NOT) integers
left shift integer
>> right shift integer >> unsigned integer
Comparison operators
== equal
!= not equal
less
less or equal
> greater
>= greater or equal
Logical operators
&& conditional AND p && q is “if p then q else false”
|| conditional OR p || q is “if p then true else q”
! NOT !p is “not p”

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)
uint8 the set of all unsigned 8-bit integers (0 to 255)
uint16 the set of all unsigned 16-bit integers (0 to 65535)
uint32 the set of all unsigned 32-bit integers (0 to 4294967295)
uint64 the set of all unsigned 64-bit integers (0 to 18446744073709551615)
int8 the set of all signed 8-bit integers (-128 to 127)
int16 the set of all signed 16-bit integers (-32768 to 32767)
int32 the set of all signed 32-bit integers (-2147483648 to 2147483647)
int64 the set of all signed 64-bit integers (-9223372036854775808 to 9223372036854775807)
float32 the set of all IEEE-754 32-bit floating-point numbers
float64 the set of all IEEE-754 64-bit floating-point numbers
complex64 the set of all complex numbers with float32 real and imaginary parts
complex128 the set of all complex numbers with float64 real and imaginary parts
byte alias for uint8

Packages

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

package math

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

package main – // Package declaration

// Multiple import statements
import “fmt”
import “time”
import “math”

// Factored import statements
import (
“fmt”
“time”
“math”
)

Comments

// Line comments
/* General comments - closed */

Reserved Keywords

break • default • func • interface • select • case • defer • go • map • struct • chan • else • goto • package • switch • const • fallthrough • if • range • type • continue • for • import • return • var

Controls

If, Else
if x > 0 {
return x
} else {
return -x
}
Loop
// Only `for`, no `while`, no `until`
for i := 1; i
}
for ; i
}
for i
}
for { // you can omit the condition ~ while (true)
}
Switch
switch tag {
default: s3()
case 0, 1, 2, 3: s1()
case 4, 5, 6, 7: s2()
}

Arrays, Slices, & Ranges

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

// the following two expressions are equivalent
make([]int, 50, 100)
new([100]int)[0:50]

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

var a [10]string
for i, s := range a {
// type of i is int
// type of s is string
// s == a[i]
g(i, s)
}

Functions

Structure
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)
 }
}
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