configure.ac: fix golang binary check

When checking the version of golang, test the major part of the string
(1.XX.yy), and fix up the error message to not mislead the minimum
version.

Fixes fvwmorg#202

configure.ac

@@ -82,18 +82,19 @@ if test ! x"$with_golang" = xno; then
 	AC_CHECK_PROGS(GO, go)
 	if test -n "$GO" ; then
 	    GOVERSIONOPTION=version
-	    go_version=$($GO $GOVERSIONOPTION | sed -e 's/go version //')
-	    AC_MSG_CHECKING([whether go version is >= 1.4.x])
-	    case $go_version in
-	    go1.[14]*)
+	    go_version=$($GO $GOVERSIONOPTION | sed -e 's/go version go//' | \
+		sed -e 's/ .*$//')
+	    AC_MSG_CHECKING([whether go version is >= 1.14.x ($go_version)])
+	    case "$go_version" in
+	     1.14*|1.15*|1.16*|1.17*|1.18*|1.19*)
 	      AC_MSG_RESULT([yes - version is: $go_version])
 	      with_golang="yes"
 	      GO=
 	      ;;
 	    *)
 	      AC_MSG_RESULT([no - version is: $go_version])
 	      with_golang="no"
-	      problem_golang=": version of go ($go_version) <= 1.4.x"
+	      problem_golang=": version of go ($go_version) <= 1.14.x"
 	      ;;
 	    esac
 	fi