Goroutine
is a lightweight thread maintained by GO runtime.
How can you convert a function to
goroutine?
You can
convert a function to Goroutine by prefixing it with the keyword ‘go’ while
calling.
Example
go
printUpperAlphabets()
In the
above example, printUpperAlphabets() method is executed as goroutine, that
means it will execute parallelly.
Let’s see
it with an example.
App.go
package main
import (
"fmt"
)
func main() {
printUpperAlphabets()
printLowerAlphabets()
}
func printUpperAlphabets() {
for alphabet := byte('A'); alphabet <= byte('Z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
func printLowerAlphabets() {
for alphabet := byte('a'); alphabet <= byte('z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
As you see
main method, I am calling two functions 'printUpperAlphabets' followed by
'printLowerAlphabets'. When I ran App.go application, I can see uppercase
alphabets followed by lowercase alphabets printed to the console.
App.go
package main
import (
"fmt"
)
func main() {
printUpperAlphabets()
printLowerAlphabets()
}
func printUpperAlphabets() {
for alphabet := byte('A'); alphabet <= byte('Z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
func printLowerAlphabets() {
for alphabet := byte('a'); alphabet <= byte('z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
Output
A B C D E
F G H I J K L M N O P Q R S T U V W X Y Z
a b c d e
f g h i j k l m n o p q r s t u v w x y z
Let’s
convert the functions printUpperAlphabets, printLowerAlphabets as goroutines
and re run App.go
Prefix
method calls with go to run them as goroutines.
go
printUpperAlphabets()
go
printLowerAlphabets()
App.go
package main
import (
"fmt"
)
func main() {
go printUpperAlphabets()
go printLowerAlphabets()
}
func printUpperAlphabets() {
for alphabet := byte('A'); alphabet <= byte('Z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
func printLowerAlphabets() {
for alphabet := byte('a'); alphabet <= byte('z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
ab
When you
ran App.go, you will not see anything. It is because, once the main function
finishes its execution, it terminates the application. Since goroutines run
parallelly, we need to give some time to the main() function to terminate.
Update
App.go by adding below statement at the end of main function.
time.Sleep(2
* time.Second)
Sleep
method makes sure that the main() pauses for 2 seconds.
App.go
package main
import (
"fmt"
"time"
)
func main() {
go printUpperAlphabets()
go printLowerAlphabets()
time.Sleep(2 * time.Second)
}
func printUpperAlphabets() {
for alphabet := byte('A'); alphabet <= byte('Z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
func printLowerAlphabets() {
for alphabet := byte('a'); alphabet <= byte('z'); alphabet++ {
fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
abc
Run App.go
for 3 or 4 times, you can see different results every time.
Run 1
a b c d e f g h i A B C D E F G H I J K L M N O P Q R S T U V W X Y j k l m n o
p q r s t u v w Z
x y z
Run 2
A a b c d
e f g h i j k l m B C D E F G H I J K L M N O P Q n o p q R S T U V W X Y Z
r s t u v
w x y z
Run 3
a b c d e
f A g h i j k l m n o p B C D q r s t u v w x y z
E F G H I
J K L M N O P Q R S T U V W X Y Z
Since
goroutines run parallelly, you are seeing different results every time.
As I said,
you can make any function as goroutine by prefixing it with go keyword, you can
run ‘fmt.Print’ also as a goroutine.
func
printUpperAlphabets() {
for alphabet := byte('A'); alphabet <=
byte('Z'); alphabet++ {
go fmt.Print(string(alphabet), "
")
}
fmt.Println()
}
How to use multi processors?
By default
all the Go applications run on single processor, if you want to utilize all the
processors, you can do it by using ‘runtime’ package.
runtime.GOMAXPROCS(8)
Above
statement sets the maximum number of CPUs to 8, that can be executing
simultaneously
App.go
package main
import (
"fmt"
"runtime"
"time"
)
func main() {
runtime.GOMAXPROCS(8)
go printUpperAlphabets()
time.Sleep(2 * time.Second)
}
func printUpperAlphabets() {
for alphabet := byte('A'); alphabet <= byte('Z'); alphabet++ {
go fmt.Print(string(alphabet), " ")
}
fmt.Println()
}
