Fix code,

src/Spinner.zig

@@ -1,76 +1,61 @@
 const std = @import("std");
-const Mutex = std.Thread.Mutex;
+const AtomicBool = std.atomic.Atomic(bool);
+const Mutex = Thread.Mutex;
+const Thread = std.Thread;
 const time = std.time;
-
 const Spinner = @This();
 
 const default_frame_rate = 150 * time.ns_per_ms;
 const default_charset = [_][]const u8{ "|", "/", "-", "\\" };
 
-// When locked, the spinner will stop spinning.
-stop_lock: Mutex,
-// Used to check if stopped.
-stopped_lock: Mutex,
+keep_going: AtomicBool,
+spinner_thread: ?Thread,
 
 // The number of nanoseconds to wait between frames.
 framerate: u64,
 
-charset: [][]const u8,
+charset: [4][]const u8,
 message: []const u8,
 
-pub fn new(framerate: ?u64, charset: ?[][]const u8, message: ?[]const u8) Spinner {
+pub fn new(framerate: ?u64, charset: ?[4][]const u8, message: ?[]const u8) Spinner {
     return Spinner{
-        .stop_lock = Mutex{},
-        .stopped_lock = Mutex{},
+        .keep_going = AtomicBool.init(false),
+        .spinner_thread = null,
         .framerate = framerate orelse default_frame_rate,
         .charset = charset orelse default_charset,
         .message = message orelse "",
     };
 }
 
-pub fn start(sp: *Spinner) void {
-    sp.stop_lock.unlock();
-    sp.stopped_lock.unlock();
-    async sp.writer();
+pub fn start(sp: *Spinner) !void {
+    sp.keep_going.store(true, .SeqCst);
+    sp.spinner_thread = try Thread.spawn(.{}, writer, .{sp});
 }
 
 pub fn stop(sp: *Spinner) void {
-    sp.stop_lock.lock();
-    sp.stopped_lock.lock();
+    sp.keep_going.store(false, .SeqCst);
+    (sp.spinner_thread orelse unreachable).join();
 }
 
-fn animateSpinnerOnce(sp: *Spinner) void {
+fn animateSpinnerOnce(sp: *Spinner) !void {
     var stdOut = std.io.getStdOut();
 
     for (sp.charset) |frame| {
-        stdOut.write(frame);
-        stdOut.write(" ");
-        stdOut.write(sp.message);
+        _ = try stdOut.write(frame);
+        _ = try stdOut.write(" ");
+        _ = try stdOut.write(sp.message);
 
         // Jumps to the start of the line.
-        stdOut.write("\r");
-        stdOut.flush();
+        _ = try stdOut.write("\r");
 
         time.sleep(sp.framerate);
     }
 }
 
-fn writer(sp: *Spinner) void {
+fn writer(sp: *Spinner) !void {
     while (true) {
-        // Stops if it has been locked by .stop().
-        if (sp.stop_lock.tryLock()) {
-            break;
-        }
-        sp.stop_lock.unlock();
+        if (!sp.keep_going.load(.SeqCst)) break;
 
-        sp.animateSpinnerOnce();
+        try sp.animateSpinnerOnce();
     }
-    sp.stopped_lock.lock();
-}
-
-test "asd" {
-    var sp = Spinner.new(null, null, "Loading...");
-    sp.start();
-    time.sleep(5 * time.ns_per_s);
-    sp.stop();
 }

zterm.zig

@@ -1 +1,11 @@
 const Spinner = @import("src/Spinner.zig");
+
+
+const time = @import("std").time;
+
+pub fn main() !void {
+    var sp = Spinner.new(null, null, "Loading...");
+    try sp.start();
+    time.sleep(5 * time.ns_per_s);
+    sp.stop();
+}