add either example

Author: ibraheemdev

futures-util/src/future/either.rs

@@ -5,8 +5,22 @@ use futures_core::stream::{FusedStream, Stream};
 #[cfg(feature = "sink")]
 use futures_sink::Sink;
 
-/// Combines two different futures, streams, or sinks having the same associated types into a single
-/// type.
+/// Combines two different futures, streams, or sinks having the same associated types into a single type.
+///
+/// This is useful when conditionally choosing between two distinct future types:
+///
+/// ```rust
+/// # use futures::future::{Either, Future};
+/// let cond = true;
+/// 
+/// let fut = if cond {
+///     Either::Left(async move { 12 })
+/// } else {
+///     Either::Right(async move { 44 })
+/// };
+///
+/// assert_eq!(fut.await, 12);
+/// ```
 #[derive(Debug, Clone)]
 pub enum Either<A, B> {
     /// First branch of the type