One limitation of the dep tool is that it does not let us use multiple major versions of a package in our projects, as each path to an imported package must be unique. The following diagram illustrates a simple scenario where packages A and B depend on the same version of package C:
Figure 3: Two packages importing the same version of the C package
Let's say now that we want to test drive v2.0.0, the new major version of the C package. The point here is to gradually update the packages importing C to import the new major version in order to assess that everything works as expected. So we update the Gopkg.toml
