private com.google.protobuf.SingleFieldBuilderV3<
            com.google.protobuf.Duration,
            com.google.protobuf.Duration.Builder,
            com.google.protobuf.DurationOrBuilder>
        getTtlFieldBuilder() {
      if (ttlBuilder_ == null) {
        if (!(expirationCase_ == 3)) {
          expiration_ = com.google.protobuf.Duration.getDefaultInstance();
        }
        ttlBuilder_ =
            new com.google.protobuf.SingleFieldBuilderV3<
                com.google.protobuf.Duration,
                com.google.protobuf.Duration.Builder,
                com.google.protobuf.DurationOrBuilder>(
                (com.google.protobuf.Duration) expiration_, getParentForChildren(), isClean());
        expiration_ = null;
      }
      expirationCase_ = 3;
      onChanged();
      return ttlBuilder_;
    }
<pre>
Desired lifetime duration of the access token. This value must
be at most 24 hours. If a value is not specified, the token's lifetime
will be set to a default value of 1 hour.
</pre>

<code>.google.protobuf.Duration ttl = 3;</code>
java-workstations/proto-google-cloud-workstations-v1beta/src/main/java/com/google/cloud/workstations/v1beta/GenerateAccessTokenRequest.java