feat: contexts support

examples/command_with_cancel.v

@@ -0,0 +1,35 @@
+import context
+import runcmd
+import time
+
+fn main() {
+	// Create context with cancel.
+	mut bg := context.background()
+	mut ctx, cancel := context.with_cancel(mut bg)
+
+	// Create new command with context.
+	mut cmd := runcmd.with_context(ctx, 'sleep', '120')
+
+	// Start a command.
+	println('Start command!')
+	cmd.start()!
+
+	// Sleep a bit for demonstration.
+	time.sleep(1 * time.second)
+
+	// Cancel command.
+	//
+	// In a real application, cancel() might be initiated by the user.
+	// For example, a command might take too long to execute and need
+	// to be canceled.
+	//
+	// See also command_with_timeout.v example.
+	println('Cancel command!')
+	cancel()
+
+	// Wait for command.
+	cmd.wait()!
+
+	// Since command has been terminated, the state would be: `signal: 15 (SIGTERM)`
+	println('Child state: ${cmd.state}')
+}