public AbstractRequestContextBuilder alloc(ByteBufAllocator alloc) {
        this.alloc = requireNonNull(alloc, "alloc");
        return this;
    }
Sets the {@link ByteBufAllocator}. If not set, {@link ByteBufAllocator#DEFAULT} is used.
core/src/main/java/com/linecorp/armeria/common/AbstractRequestContextBuilder.java