travis, build: enable Ubuntu Focal and Go 1.13.6 on PPA

.travis.yml

@@ -93,7 +93,7 @@ jobs:
             - python-paramiko
       script:
         - echo '|1|7SiYPr9xl3uctzovOTj4gMwAC1M=|t6ReES75Bo/PxlOPJ6/GsGbTrM0= ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA0aKz5UTUndYgIGG7dQBV+HaeuEZJ2xPHo2DS2iSKvUL4xNMSAY4UguNW+pX56nAQmZKIZZ8MaEvSj6zMEDiq6HFfn5JcTlM80UwlnyKe8B8p7Nk06PPQLrnmQt5fh0HmEcZx+JU9TZsfCHPnX7MNz4ELfZE6cFsclClrKim3BHUIGq//t93DllB+h4O9LHjEUsQ1Sr63irDLSutkLJD6RXchjROXkNirlcNVHH/jwLWR5RcYilNX7S5bIkK8NlWPjsn/8Ua5O7I9/YoE97PpO6i73DTGLh5H9JN/SITwCKBkgSDWUt61uPK3Y11Gty7o2lWsBjhBUm2Y38CBsoGmBw==' >> ~/.ssh/known_hosts
-        - go run build/ci.go debsrc -goversion 1.13.4 -upload ethereum/ethereum -sftp-user geth-ci -signer "Go Ethereum Linux Builder <geth-ci@ethereum.org>"
+        - go run build/ci.go debsrc -goversion 1.13.6 -upload ethereum/ethereum -sftp-user geth-ci -signer "Go Ethereum Linux Builder <geth-ci@ethereum.org>"
 
     # This builder does the Linux Azure uploads
     - stage: build

build/checksums.txt

@@ -1,6 +1,6 @@
 # This file contains sha256 checksums of optional build dependencies.
 
-95dbeab442ee2746b9acf0934c8e2fc26414a0565c008631b04addb8c02e7624  go1.13.4.src.tar.gz
+aae5be954bdc40bcf8006eb77e8d8a5dde412722bc8effcdaf9772620d06420c  go1.13.6.src.tar.gz
 
 1fcbc9e36f4319eeed02beb8cfd1b3d425ffc2f90ddf09a80f18d5064c51e0cb  golangci-lint-1.21.0-linux-386.tar.gz
 267b4066e67139a38d29499331a002d6a29ad5be7aafc83db3b1e88f1b027f90  golangci-lint-1.21.0-linux-armv6.tar.gz

build/ci.go

@@ -145,6 +145,7 @@ var (
 		"bionic": "golang-go",
 		"disco":  "golang-go",
 		"eoan":   "golang-go",
+		"focal":  "golang-go",
 	}
 
 	debGoBootPaths = map[string]string{