You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/firezone/rust/connlib/shared/src
    
    the code of the file until where you have to start completion: //! This crates contains shared types and behavior between all the other libraries.
//!
//! This includes types provided by external crates, i.e. [boringtun] to make sure that
//! we are using the same version across 
    
fn kernel_version() -> Option<String> {
    #[cfg(any(target_os = "android", target_os = "linux"))]
    let mut utsname = libc::utsname {
        sysname: [0; 65],
        nodename: [0; 65],
        release: [0; 65],
        version: [0; 65],
        machine: [0; 65],
        domainname: [0; 65],
    };

    #[cfg(any(target_os = "macos", target_os = "ios"))]
    let mut utsname = libc::utsname {
        sysname: [0; 256],
        nodename: [0; 256],
        release: [0; 256],
        version: [0; 256],
        machine: [0; 256],
    };

    // SAFETY: we just allocated the pointer
    if unsafe { libc::uname(&mut utsname as *mut _) } != 0 {
        return None;
    }

    #[cfg_attr(
        all(target_os = "linux", target_arch = "aarch64"),
        allow(clippy::unnecessary_cast)
    )]
    let version: Vec<u8> = utsname
        .release
        .split(|c| *c == 0)
        .next()?
        .iter()
        .map(|x| *x as u8)
        .collect();

    String::from_utf8(version).ok()
}