Upgrade go-jose to 2.4.0.

go.mod

@@ -37,5 +37,5 @@ require (
 	golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e // indirect
 	google.golang.org/appengine v1.5.0 // indirect
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
-	gopkg.in/square/go-jose.v2 v2.3.1
+	gopkg.in/square/go-jose.v2 v2.4.0
 )

go.sum

@@ -111,7 +111,7 @@ google.golang.org/appengine v1.5.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/square/go-jose.v2 v2.3.1 h1:SK5KegNXmKmqE342YYN2qPHEnUYeoMiXXl1poUlI+o4=
-gopkg.in/square/go-jose.v2 v2.3.1/go.mod h1:M9dMgbHiYLoDGQrXy7OpJDJWiKiU//h+vD76mk0e1AI=
+gopkg.in/square/go-jose.v2 v2.4.0 h1:0kXPskUMGAXXWJlP05ktEMOV0vmzFQUWw6d+aZJQU8A=
+gopkg.in/square/go-jose.v2 v2.4.0/go.mod h1:M9dMgbHiYLoDGQrXy7OpJDJWiKiU//h+vD76mk0e1AI=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=