fix: map keyfile as shared

src/main.rs

@@ -1,4 +1,6 @@
-use libc::{c_int, c_void, mmap, MAP_FAILED, MAP_SHARED, PROT_READ, PROT_WRITE};
+use libc::{
+    c_char, c_int, c_void, mmap, perror, MAP_FAILED, MAP_PRIVATE, MAP_SHARED, PROT_READ, PROT_WRITE,
+};
 use std::fs::File;
 use std::os::fd::AsRawFd;
 use std::{env, ptr};
@@ -45,7 +47,12 @@ fn main() {
     } as *mut u8;
     assert_ne!(sync_memory, MAP_FAILED as *mut u8);
 
-    let private_file = File::open(&args[2]).expect("Cannot open KEY_FILE");
+    let private_file = File::options()
+        .read(true)
+        .write(true)
+        .open(&args[2])
+        .expect("Cannot open KEY_FILE");
+
     let private_mem = unsafe {
         mmap(
             ptr::null_mut() as *mut c_void,