[skip ci]Add retry comment (#8776)

Signed-off-by: godchen <qingxiang.chen@zilliz.com>

internal/util/retry/options.go

@@ -27,14 +27,17 @@ func newDefaultConfig() *config {
 	}
 }
 
+// Option is used to config the retry function.
 type Option func(*config)
 
+// Attempts is used to config the max retry times.
 func Attempts(attempts uint) Option {
 	return func(c *config) {
 		c.attempts = attempts
 	}
 }
 
+// Sleep is used to config the initial interval time of each execution.
 func Sleep(sleep time.Duration) Option {
 	return func(c *config) {
 		c.sleep = sleep
@@ -45,6 +48,7 @@ func Sleep(sleep time.Duration) Option {
 	}
 }
 
+// MaxSleep is used to config the max interval time of each execution.
 func MaxSleepTime(maxSleepTime time.Duration) Option {
 	return func(c *config) {
 		// ensure max retry interval is always larger than retry interval

internal/util/retry/retry.go

@@ -18,6 +18,9 @@ import (
 	"time"
 )
 
+// Do will run function with retry mechanism.
+// fn is the func to run.
+// Option can control the retry times and timeout.
 func Do(ctx context.Context, fn func() error, opts ...Option) error {
 
 	c := newDefaultConfig()
@@ -79,6 +82,7 @@ func Unrecoverable(err error) error {
 	return unrecoverableError{err}
 }
 
+// IsUncoverable is used to judge whether the error is wrapped by unrecoverableError.
 func IsUncoverable(err error) bool {
 	_, isUnrecoverable := err.(unrecoverableError)
 	return isUnrecoverable