backend: fix doc typos

backend/local/local.go

@@ -240,7 +240,7 @@ func (b *Local) Remove(t backend.Type, name string) error {
 }
 
 // List returns a channel that yields all names of blobs of type t. A
-// goroutine ist started for this. If the channel done is closed, sending
+// goroutine is started for this. If the channel done is closed, sending
 // stops.
 func (b *Local) List(t backend.Type, done <-chan struct{}) <-chan string {
 	// TODO: use os.Open() and d.Readdirnames() instead of Glob()

backend/s3/s3.go

@@ -41,7 +41,7 @@ func OpenS3Bucket(bucket *s3.Bucket, bucketname string) *S3Backend {
 	return &S3Backend{bucket: bucket, path: bucketname, connChan: connChan}
 }
 
-// Open opens the s3 backend at bucket and region.
+// Open opens the S3 backend at bucket and region.
 func Open(regionname, bucketname string) (backend.Backend, error) {
 	auth, err := aws.EnvAuth()
 	if err != nil {

backend/sftp/sftp.go

@@ -372,7 +372,7 @@ func (r *SFTP) Remove(t backend.Type, name string) error {
 }
 
 // List returns a channel that yields all names of blobs of type t. A
-// goroutine ist started for this. If the channel done is closed, sending
+// goroutine is started for this. If the channel done is closed, sending
 // stops.
 func (r *SFTP) List(t backend.Type, done <-chan struct{}) <-chan string {
 	ch := make(chan string)