README.md: update gethostname api

Author: Mic92

README.md

@@ -26,8 +26,8 @@ call:
 // libc api (unsafe, requires handling return code/errno)
 pub unsafe extern fn gethostname(name: *mut c_char, len: size_t) -> c_int;
 
-// nix api (returns a nix::Result)
-pub fn gethostname(name: &mut [u8]) -> Result<()>;
+// nix api (returns a nix::Result<CStr>)
+pub fn gethostname<'a>(buffer: &'a mut [u8]) -> Result<&'a CStr>;
 ```
 
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