Update .travis.yml

.travis.yml

@@ -6,6 +6,8 @@ language: cpp
 
 sudo: false
 
+dist: trusty
+
 branches:
   only:
     - master
@@ -116,6 +118,16 @@ matrix:
           sources:
             - ubuntu-toolchain-r-test
 
+    - os: linux
+      compiler: g++-9
+      env: TOOLSET=gcc COMPILER=g++-9 CXXSTD=03,11,14,17,2a
+      addons:
+        apt:
+          packages:
+            - g++-9
+          sources:
+            - ubuntu-toolchain-r-test
+
     - os: linux
       compiler: clang++
       env: TOOLSET=clang COMPILER=clang++ CXXSTD=03,11
@@ -238,6 +250,17 @@ matrix:
             - ubuntu-toolchain-r-test
             - llvm-toolchain-trusty-7
 
+    - os: linux
+      compiler: clang++-8
+      env: TOOLSET=clang COMPILER=clang++-8 CXXSTD=03,11,14,17,2a
+      addons:
+        apt:
+          packages:
+            - clang-8
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-8
+
     - os: linux
       compiler: clang++-libc++
       env: TOOLSET=clang COMPILER=clang++-libc++ CXXSTD=03,11,14,1z VARIANT=release