Pray how did you manage to do it?'

    `In my youth,' said his father, `I took to the law,
      And argued each case with my wife;
    And the muscular strength, which it gave to my jaw,
      Has lasted the rest of my life.'

    `You are old,' said the youth, `one would hardly suppose
      That your eye was as steady as ever;

      Pray how did you manage to do it?'

    `In my youth,' said his father, `I took to the law,
      And argued each case with my wife;
    And the muscular strength, which it gave to my jaw,
      Has lasted the rest of my life.'

    `You are old,' said the youth, `one would hardly suppose
      That your eye was as steady as ever;

"crypto/internal/fips140" "crypto/internal/fips140/aes" "crypto/internal/fips140/subtle" "crypto/internal/fips140deps/byteorder" "math/bits" ) // Counter is an SP 800-90A Rev. 1 CTR_DRBG instantiated with AES-256. // // Per Table 3, it has a security strength of 256 bits, a seed size of 384 bits, // a counter length of 128 bits, a reseed interval of 2^48 requests, and a // maximum request size of 2^19 bits (2^16 bytes, 64 KiB). // // We support a narrow range of parameters that fit the needs of our RNG:...

            final byte[] ntResponse = getNTResponse();
            final int ntLength = ntResponse != null ? ntResponse.length : 0;
            final byte[] sessionKey = getSessionKey();
            final int keyLength = sessionKey != null ? sessionKey.length : 0;
            final byte[] type3 = new byte[64 + domainLength + userLength + workstationLength + lmLength + ntLength + keyLength];
            System.arraycopy(NTLMSSP_SIGNATURE, 0, type3, 0, 8);

"crypto/internal/fips140" "crypto/internal/fips140/aes" "crypto/internal/fips140/subtle" "crypto/internal/fips140deps/byteorder" "math/bits" ) // Counter is an SP 800-90A Rev. 1 CTR_DRBG instantiated with AES-256. // // Per Table 3, it has a security strength of 256 bits, a seed size of 384 bits, // a counter length of 128 bits, a reseed interval of 2^48 requests, and a // maximum request size of 2^19 bits (2^16 bytes, 64 KiB). // // We support a narrow range of parameters that fit the needs of our RNG:...

because it documents the full list of known GODEBUG settings,
which are tied to a specific release.
-->

## Introduction {#intro}

Go's emphasis on backwards compatibility is one of its key strengths.
There are, however, times when we cannot maintain complete compatibility.
If code depends on buggy (including insecure) behavior,
then fixing the bug will break that code.
New features can also have similar impacts: