fix the links in README

Author: yashbhutwala

.gitignore

@@ -20,3 +20,6 @@ _cgo_export.*
 _testmain.go
 
 *.exe
+
+# IDEs
+.idea/

README.md

@@ -11,16 +11,15 @@ The retries exponentially increase and stop increasing when a certain threshold
 
 Import path is `github.com/cenkalti/backoff/v4`. Please note the version part at the end.
 
-godoc.org does not support modules yet,
-so you can use https://godoc.org/gopkg.in/cenkalti/backoff.v4 to view the documentation.
+Use https://pkg.go.dev/github.com/cenkalti/backoff/v4 to view the documentation.
 
 ## Contributing
 
 * I would like to keep this library as small as possible.
 * Please don't send a PR without opening an issue and discussing it first.
 * If proposed change is not a common use case, I will probably not accept it.
 
-[godoc]: https://godoc.org/github.com/cenkalti/backoff
+[godoc]: https://pkg.go.dev/github.com/cenkalti/backoff/v4
 [godoc image]: https://godoc.org/github.com/cenkalti/backoff?status.png
 [travis]: https://travis-ci.org/cenkalti/backoff
 [travis image]: https://travis-ci.org/cenkalti/backoff.png?branch=master
@@ -30,4 +29,4 @@ so you can use https://godoc.org/gopkg.in/cenkalti/backoff.v4 to view the docume
 [google-http-java-client]: https://github.com/google/google-http-java-client/blob/da1aa993e90285ec18579f1553339b00e19b3ab5/google-http-client/src/main/java/com/google/api/client/util/ExponentialBackOff.java
 [exponential backoff wiki]: http://en.wikipedia.org/wiki/Exponential_backoff
 
-[advanced example]: https://godoc.org/github.com/cenkalti/backoff#example_
+[advanced example]: https://pkg.go.dev/github.com/cenkalti/backoff/v4?tab=doc#pkg-examples