I updated one of my servers from Go 1 to Go tip and it now fails to start:

Listen: Failed to load TLS keypair (cert="/home/bradfitz/keys/xx/ssl.crt",
key="/home/bradfitz/keys/xx/ssl.key"): crypto/tls: failed to parse key PEM data

That error comes from crypto/tls.X509KeyPair:

func X509KeyPair(certPEMBlock, keyPEMBlock []byte) (cert Certificate, err error) {
....
        var keyDERBlock *pem.Block
        for {
                keyDERBlock, keyPEMBlock = pem.Decode(keyPEMBlock)
                if keyDERBlock == nil {
                        err = errors.New("crypto/tls: failed to parse key PEM data")
                        return
                }
...


Without attaching my private key to this bug, here's some debugging I added to
pem.Decode:

func Decode(data []byte) (p *Block, rest []byte) {
        println("call pem: decode of ", len(data), "bytes")
        defer func() {
                println(" ret decoded = ", p != nil, "rest=", len(rest))
        }()
        // pemStart begins with a newline. However, at the very beginning of
        // the byte array, we'll accept the start string without it.
        rest = data
        if bytes.HasPrefix(data, pemStart[1:]) {
                rest = rest[len(pemStart)-1 : len(data)]
        } else if i := bytes.Index(data, pemStart); i >= 0 {
                rest = rest[i+len(pemStart) : len(data)]
        } else {
                println("nil data")     // hitting this
                return nil, data
        }

call pem: decode of  7862 bytes
 ret decoded =  true rest= 4972
call pem: decode of  4972 bytes
 ret decoded =  true rest= 2760
call pem: decode of  2760 bytes
 ret decoded =  true rest= 0
call pem: decode of  0 bytes
nil data
 ret decoded =  false rest= 0
call pem: decode of  3272 bytes
 ret decoded =  true rest= 0
call pem: decode of  0 bytes
nil data
 ret decoded =  false rest= 0
Listen: Failed to load TLS keypair (cert="/home/bradfitz/keys/xxx/ssl.crt",
key="/home/bradfitz/keys/xxx/ssl.key"): crypto/tls: failed to parse key PEM
data