public long tlsHandshakeDurationNanos() {
        return tlsHandshakeDurationNanos;
    }
Returns the duration which was taken to TLS handshake, in nanoseconds.

@return the duration, or {@code -1} if there was no action to TLS handshake.
core/src/main/java/com/linecorp/armeria/common/logging/ClientConnectionTimings.java