document error introduced by timeouts

src/docs/goose-book/src/getting-started/tips.md

@@ -1,4 +1,26 @@
 # Tips
 
+## Best Practices
+
 * When writing load tests, avoid [`unwrap()`](https://doc.rust-lang.org/std/option/enum.Option.html#method.unwrap) (and variations) in your task functions -- Goose generates a lot of load, and this tends to trigger errors. Embrace Rust's warnings and properly handle all possible errors, this will save you time debugging later.
 * When running your load test, use the cargo `--release` flag to generate optimized code. This can generate considerably more load test traffic. Learn more about this and other optimizations in ["The golden Goose egg, a compile-time adventure"](https://www.tag1consulting.com/blog/golden-goose-egg-compile-time-adventure).
+
+## Errors
+
+### Timeouts
+
+By default, Goose will time out requests that take longer than 60 seconds to return, and display a `WARN` level message saying, "operation timed out". For example:
+
+```
+11:52:17 [WARN] "/node/3672": error sending request for url (http://apache/node/3672): operation timed out
+```
+
+These will also show up in the error summary displayed with the final metrics. For example:
+
+```
+ 51            GET (Auth) comment form: error sending request (Auth) comment form: operation timed out
+```
+
+To change how long before requests time out, use `--timeout VALUE` when starting a load test, for example `--timeout 30` will time out requests that take longer than 30 seconds to return. To configure the timeout programatically, use [`.set_default()`](https://docs.rs/goose/*/goose/config/trait.GooseDefaultType.html#tymethod.set_default) to set [GooseDefault::Timeout](https://docs.rs/goose/*/goose/config/enum.GooseDefault.html#variant.Timeout).
+
+To completely disable timeouts, you must build a custom Reqwest Client with [`GooseUser::set_client_builder`](https://docs.rs/goose/*/goose/goose/struct.GooseUser.html#method.set_client_builder). Alternatively, you can just set a very high timeout, for example `--timeout 86400` will let a request take up to 24 hours.