Function stop 

pub fn stop<W>(buf: &mut [u8], write: W, uid: u32) -> Result<(), EspError>
where
    W: FnMut(&[u8]) -> Result<(), EspError>,

Stop WiFi If mode is WIFI_MODE_STA, it stops station and frees station control block If mode is WIFI_MODE_AP, it stops soft-AP and frees soft-AP control block If mode is WIFI_MODE_APSTA, it stops station/soft-AP and frees station/soft-AP control block If mode is WIFI_MODE_NAN, it stops NAN and frees NAN control block. docs