fix example #480

Job	Run time
cmake	51s
aarch64	1m 41s
arenastring-gcc-stdlibc++-default	27s
basic-gcc-dbg-c++20-stdlibc++-asan	45s
arenastring-gcc-stdlibc++-half	30s
basic-gcc-dbg-c++20-stdlibc++-tsan	37s
compatible-gcc-9	39s
coverage	46s
basic-gcc-dbg-c++14-stdlibc++-asan	51s
basic-gcc-opt-c++20-stdlibc++-asan	39s
arenastring-gcc-stdlibc++-full	28s
cpp14-coroutine	29s
basic-gcc-opt-c++20-stdlibc++-tsan	29s
arenastring-clang-stdlibc++-default	32s
workspace	25s
basic-gcc-opt-c++14-stdlibc++-asan	31s
arenastring-clang-libc++-default	34s
basic-clang-dbg-c++20-stdlibc++-asan	36s
basic-clang-dbg-c++20-stdlibc++-tsan	56s
basic-clang-dbg-c++20-libc++-asan	49s
basic-clang-dbg-c++20-libc++-tsan	51s
basic-clang-dbg-c++14-stdlibc++-asan	39s
basic-clang-dbg-c++14-libc++-asan	42s
basic-clang-opt-c++20-stdlibc++-asan	38s
basic-clang-opt-c++20-stdlibc++-tsan	32s
basic-clang-opt-c++20-libc++-asan	37s
basic-clang-opt-c++20-libc++-tsan	34s
basic-clang-opt-c++14-stdlibc++-asan	50s
basic-clang-opt-c++14-libc++-asan	41s
	19m 39s

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