Issue 1766 Modified mustache files for Go to support nullable in the … (#1869)

* Issue 1766 Modified mustache files for Go to support nullable in the spec v3.0+; Updated model files running .sh scripts for Go.

* Add "nullable" to fake yaml

* Add sample script for OAS3

* Fix output folder (openapi3)

* Run bin/openapi3/go-petstore.sh

* Update samples

* Update jaxrs-jersey

* Update python and php samples

* Add bin/openapi3/go-gin-petstore-server.sh

* Run bin/openapi3/go-gin-petstore-server.sh

* Update bin/openapi3/go-petstore-server.sh to generate "nullable" samples

* Run bin/openapi3/go-petstore-server.sh

* Fix duplicated `import`

samples/server/openapi3/petstore/python-flask-python2/setup.py

@@ -0,0 +1,40 @@
+# coding: utf-8
+
+import sys
+from setuptools import setup, find_packages
+
+NAME = "openapi_server"
+VERSION = "1.0.0"
+
+# To install the library, run the following
+#
+# python setup.py install
+#
+# prerequisite: setuptools
+# http://pypi.python.org/pypi/setuptools
+
+REQUIRES = [
+    "connexion==2.0.0",
+    "swagger-ui-bundle==0.0.2",
+    "python_dateutil==2.6.0",
+    "typing==3.5.2.2"
+]
+
+setup(
+    name=NAME,
+    version=VERSION,
+    description="OpenAPI Petstore",
+    author_email="",
+    url="",
+    keywords=["OpenAPI", "OpenAPI Petstore"],
+    install_requires=REQUIRES,
+    packages=find_packages(),
+    package_data={'': ['openapi/openapi.yaml']},
+    include_package_data=True,
+    entry_points={
+        'console_scripts': ['openapi_server=openapi_server.__main__:main']},
+    long_description="""\
+    This is a sample server Petstore server. For this sample, you can use the api key `special-key` to test the authorization filters.
+    """
+)
+