By default, Rust programs will unwind the stack when a panic! happens. If you'd prefer an immediate abort instead, you can configure this in Cargo.toml:

[profile.dev]
panic = "abort"

[profile.release]
panic = "abort"

Why might you choose to do this? By removing support for unwinding, you'll get smaller binaries. You will lose the ability to catch panics. Which choice is right for you depends on exactly what you're doing.