io: Add example to io.Seeker's Seek() method.

While there's an example for SectionReader.Seek, if someone is
seeking documentation specifically about Seeker.Seek, they may
not immediately find the SectionReader example. Offset and whence
may not be entirely intuitive to new developers either, so include
examples of both positive/negative offsets and SeekStart/SeekEnd.

Change-Id: I5b7442ccf683d9706e9261c11bc0ea31a1ac21d4
Reviewed-on: https://go-review.googlesource.com/48873
Reviewed-by: Kevin Burke <kev@inburke.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/io/example_test.go b/src/io/example_test.go
index bf16de8fe2357d4d890fa0710a9974c198591048..af4785372679ad056791697182cbb689164ae145 100644 (file)
--- a/src/io/example_test.go
+++ b/src/io/example_test.go
@@ -204,6 +204,28 @@ func ExampleSectionReader_Seek() {
        // stream
 }
 
+func ExampleSeeker_Seek() {
+       r := strings.NewReader("some io.Reader stream to be read\n")
+       if _, err := io.Copy(os.Stdout, r); err != nil {
+               log.Fatal(err)
+       }
+
+       r.Seek(15, io.SeekStart)
+       if _, err := io.Copy(os.Stdout, r); err != nil {
+               log.Fatal(err)
+       }
+
+       r.Seek(-5, io.SeekEnd)
+       if _, err := io.Copy(os.Stdout, r); err != nil {
+               log.Fatal(err)
+       }
+
+       // Output:
+       // some io.Reader stream to be read
+       // stream to be read
+       // read
+}
+
 func ExampleMultiWriter() {
        r := strings.NewReader("some io.Reader stream to be read\n")