all: example suffixes should start with a lower case letter

GoDoc example suffixes should start with a lower case letter.

```
// ... The suffix may be
// absent. Otherwise, it must start with a lower-case letter and
// be preceded by '_'.
```

https://golang.org/src/go/doc/example.go