andrewchambers · August 28, 2018 23:07 · Aug 28, 2018 · Aug 28, 2018 · Aug 28, 2018
diff --git a/errors.md b/errors.md
@@ -1,7 +1,8 @@
-My observation is that a root cause of an error is special, most values in the
-error chain are only used except to preserve line information. Users
-and debuggers usually only care about the first error and the last
-error in the chain. In the end I disliked pkg/errors naming conventions and
+My observation is that a root cause of an error is special,
+I usually only care about the first error and the last
+error in the chain except for logs. 
+
+In the end I disliked pkg/errors naming conventions and 
 wrote my own small package.
 
 A typical usage of my package in a server:

diff --git a/errors.md b/errors.md
@@ -1,8 +1,8 @@
-In my own code, I use my own error package. My observation
-is that a root cause of an error is special, most values in the
-error chain are useless except to preserve line information. Users
+My observation is that a root cause of an error is special, most values in the
+error chain are only used except to preserve line information. Users
 and debuggers usually only care about the first error and the last
-error in the chain.
+error in the chain. In the end I disliked pkg/errors naming conventions and
+wrote my own small package.
 
 A typical usage of my package in a server:
 

diff --git a/errors.md b/errors.md
@@ -0,0 +1,31 @@
+In my own code, I use my own error package. My observation
+is that a root cause of an error is special, most values in the
+error chain are useless except to preserve line information. Users
+and debuggers usually only care about the first error and the last
+error in the chain.
+
+A typical usage of my package in a server:
+
+```
+err := errors.Wrapf(err, "Additional context: %s", s)
+...
+if errors.RootCause(err) != sql.ErrNoRows {
+  Log("an error happend", "trace", errors.Trace(err))
+}
+```
+
+A typical usage in a cli application is:
+
+```
+...
+if err != nil {
+  // err.Error() only cares about the top level error and the root cause
+  fmt.Fprintf(os.Stderr, "%s\n", err.Error()) // 'Init failed' caused by 'File foo.cfg does not exist'
+  os.Exit(1)
+}
+
+```
+
+One big lack I found is knowing the possible values of RootCause... A Go guru
+like analysis may help. especially a way to check reality with what the 
+doc comments say.
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