fix: map keyfile as shared

src/main.rs

@@ -1,6 +1,4 @@
-use libc::{
-    c_int, c_void, mmap, MAP_FAILED, MAP_PRIVATE, MAP_SHARED, PROT_READ, PROT_WRITE,
-};
+use libc::{c_int, c_void, mmap, MAP_FAILED, MAP_SHARED, PROT_READ, PROT_WRITE};
 use std::fs::File;
 use std::os::fd::AsRawFd;
 use std::{env, ptr};
@@ -53,7 +51,7 @@ fn main() {
             ptr::null_mut() as *mut c_void,
             32 * 100,
             PROT_READ | PROT_WRITE,
-            MAP_PRIVATE,
+            MAP_SHARED,
             private_file.as_raw_fd(),
             0,
         )