08. Hello, World!

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08. Hello, World!
Go Program Order
package statement
imports statement
functions, variables, constants etc.
main.go
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package main
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​
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import "fmt"
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​
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func main() {
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	fmt.Println("Hello, Pune!")
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}
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Package statement
each go file must start with package declaration.
package is the keyword used to declare a package.
main.go
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package main
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packages are used modularity, encapsulation, separate compilation, and reuse.
Go comes with lot of in-build library packages
Standard library - pkg.go.dev
crypto - cryptography related code.
fmt - formatted input/output related code.
os - operation system related code.
net/http - http related code.
Import statement
import statements are used to import external packages.
import is the keyword used to import a package.
main.go
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import "fmt"
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before using functionality provided by any package, it needs to be imported.
multiple packages can be imported using single import clause.
main.go
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import (
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	"fmt"
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	"net/http"
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	"os"
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)
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unused imports are not allowed.
Main package
declaring a main package is way to telling Go that this is executable and not library.
Main package should have method named main for Go to be able to execute it.
effectively, main is starting point for application to run from a functionality point of view.
main.go
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func main() {
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	fmt.Println("Hello, Pune!")
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}
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Declaring a function
function is a code block that can be called by name.
a function is declared using func keyword followed by name of function.
function name should be followed by round brackets ()
every function should have function body. This is defined using opening and closing curly braces {}
ideally, function can accept input in the form of function parameters and return output in form of return values.
main.go
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func sayHello() {
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	fmt.Println("Hello, Pune!")
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}
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Calling a function
function that are in same package can be called directly by name.
function is called using function name followed by ()
functions in other packages needs to be called using package name followed by dot . and followed by function name.
main.go
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func sayHello() {
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	fmt.Println("Hello, Pune!")
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}
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func main() {
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	sayHello()
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}
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Identify all the function call in code snippet below.
main.go
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package main
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​
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import "fmt"
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​
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func sayHello() {
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	fmt.Println("Hello, Pune!")
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}
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func main() {
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	sayHello()
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	fmt.Println("Getting started is so easy")
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	fmt.Println("And fun!")
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}
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The Go Playground
Guess the output
main.go
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package main
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​
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import "fmt"
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​
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func main() 
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{
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	fmt.Println("Hello, Pune!")
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}
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Opening Brace must be on same line where function starts.
07. Go Playground
09. Installing Go
Last modified 2yr ago
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