Learning Go through a course in Coursera

Recently, my friend, Eduard, suggested learning Golang. Go is an interesting language with powerful low-level features like pointer but also with modern language support like garbage collection.

I used brew to install Go, as I’m on mac.

brew install golang

Hello world

package main

import "fmt"

func main() {
	fmt.Println("Hello world")
}

import bring in package. In go, everything is package. fmt is like Console in c#

To run it, do go run hello.go

conditionals

// if else
func NewName(fname string, lname string) *Name {
	name := new(Name)
	if len(fname) > 20 {
		name.fname = fname[:20]
	} else {
		name.fname = fname
	}

	if len(lname) > 20 {
		name.lname = lname[:20]
	} else {
		name.lname = lname
	}

	return name
}

handling strings

package main

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

func main() {

	fmt.Println("Enter your string input")
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	input := scanner.Text()

	var inputLowercase = strings.ToLower(input)
	var userInputBody = inputLowercase[1:len(inputLowercase)-1]

	if strings.HasPrefix(inputLowercase, "i") &&
		strings.HasSuffix(inputLowercase, "n") &&
		strings.Contains(userInputBody, "a") {

		fmt.Println("Found!")
	} else {
		fmt.Println("Not Found!")
	}

}

bufio is to receive user input that includes space. string is a collection of character. [0:10] syntax was really powerful.

iterations

// for range
var names []Name
for fileScanner.Scan() {
	nameArr := strings.Split(fileScanner.Text(), " ")
	name := NewName(nameArr[0], nameArr[1])
	names = append(names, *name)
}

for _, name := range names {
	fmt.Printf("%s %s\n", name.fname, name.lname)
}

json

	scanner := bufio.NewScanner(os.Stdin)
	user := make(map[string]string)

	fmt.Println("Enter your name")
	scanner.Scan()
	user["name"] = scanner.Text()

	fmt.Println("Enter your address")
	scanner.Scan()
	user["address"] = scanner.Text()

	jsonString, _ := json.Marshal(user)
	fmt.Println(string(jsonString))

map

scanner := bufio.NewScanner(os.Stdin)
user := make(map[string]string)

fmt.Println("Enter your name")
scanner.Scan()
user["name"] = scanner.Text()

fmt.Println("Enter your address")
scanner.Scan()
user["address"] = scanner.Text()

slice

a dynamically-sized flexible view into the elements of an array

var names []Name
for fileScanner.Scan() {
	nameArr := strings.Split(fileScanner.Text(), " ")
	name := NewName(nameArr[0], nameArr[1])
	names = append(names, *name)
}

string

// cut up to the length
func NewName(fname string, lname string) *Name {
	name := new(Name)
	name.fname = fname[:20]
	name.lname = lname[:20]

	return name
}

// split
nameArr := strings.Split(fileScanner.Text(), " ")
name := NewName(nameArr[0], nameArr[1])

struct

struct is a typed collection of fields, usefl for grouping data together to form records

type person struct {
    name string
    age  int
}

s := person{name: "Sean", age: 50}

truncate fractional digits to int value

By doing this assignment, I learned stdin, number conversion, and Println format.

package main

import "fmt"

func main() {
	var input float64
	var number int

	fmt.Println("Enter your floating number")
	fmt.Scanln(&input)

	number = int(input)
	fmt.Printf("Your int value is %d\n", number)
}

Scanln accepts user input. Yet it can’t handle space so you need to use bufio if the input has any space in it.

user input

simple string without space

var firstname string
fmt.Println("your firstname: ")
fmt.Scanln(&firstname)

If you the input has space in the middle, use Scanner

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

func main() {
	scanner := bufio.NewScanner(os.Stdin)

	fmt.Println("Enter your name")
	scanner.Scan()
	name := scanner.Text()
}