Waitgroup usage examples in the Go Language Sync pack

Waitgroup

It can wait until all the goroutine execute and block the execution of the main thread until all the Goroutine execution is complete.

Waitgroup a total of three methods

Add: Adds or reduces the number of waiting goroutine
Done: Equivalent to add (-1)
Wait: Perform blocking until all the Waitgroup number becomes 0

Practice

Example 1 differs from Instance 2 code: One line of code is missing go func () {} ()
Example 1 and instance 3 code differences: Runtime. Gomaxprocs's entry is different.

Example 1 (sequential output)

Package Mainimport ("FMT" "Sync" "Runtime") func main () {N: = The runtime. Gomaxprocs (1) var waitgroup sync. Waitgroup Waitgroup.add (2*n) for I: = 1; I <= N; i++ {go func (i int) {//defer Waitgroup.add                                                ( -1) defer waitgroup.done () Fmt. Printf ("%c", + + i)} (i)} for I: = 1; I <= N; i++ {go func (i int) {//defer waitgroup.ad                                                D ( -1) defer waitgroup.done () Fmt.      Printf ("%c", + i)} (i)} go func () {} ()          Waitgroup.wait ()} 

Run results

Example 2 (except for the last letter, other character sequential output)

Package Mainimport ("FMT" "Sync" "Runtime") func main () {N: = The runtime. Gomaxprocs (1) var waitgroup sync. Waitgroup Waitgroup.add (2*n) for I: = 1; I <= N; i++ {go func (i int) {//defer Waitgroup.add                                                ( -1) defer waitgroup.done () Fmt. Printf ("%c", + + i)} (i)} for I: = 1; I <= N; i++ {go func (i int) {//defer waitgroup.ad                                                D ( -1) defer waitgroup.done () Fmt.    Printf ("%c", + i)} (i)}//go func () {} ()            Waitgroup.wait ()} 

Run results
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 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

Example 3 (out of sequence output)

Package Mainimport ("FMT" "Sync" "Runtime") func main () {N: = The runtime. Gomaxprocs (2) var waitgroup sync. Waitgroup Waitgroup.add (2*n) for I: = 1; I <= N; i++ {go func (i int) {//defer Waitgroup.add                                                ( -1) defer waitgroup.done () Fmt. Printf ("%c", + + i)} (i)} for I: = 1; I <= N; i++ {go func (i int) {//defer waitgroup.ad                                                D ( -1) defer waitgroup.done () Runtime. Gosched () fmt.                        Printf ("%c", + i)        } (i)} go func () {} () waitgroup.wait ()} 

Run results

Waitgroup usage examples in the Go Language Sync pack