[skywalking-nodejs] 01/01: Polish the readme to clarify the init options

[ke...@apache.org]

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kezhenxu94 pushed a commit to branch doc/init
in repository https://gitbox.apache.org/repos/asf/skywalking-nodejs.git

commit 8484f3c94bd0b958f9818a917f8a5e3bd6be92ee
Author: kezhenxu94 <ke...@apache.org>
AuthorDate: Wed Dec 30 23:45:46 2020 +0800

    Polish the readme to clarify the init options
---
 README.md | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/README.md b/README.md
index 541215a..bcb42e3 100644
--- a/README.md
+++ b/README.md
@@ -20,15 +20,25 @@ SkyWalking NodeJS SDK requires SkyWalking backend (OAP) 8.0+ and NodeJS >= 10.
 ```typescript
 import agent from 'skywalking';
 
+agent.start();
+```
+
+This will use default configurations to start the SkyWalking agent above, if you want to specify your own configurations, here are two methods.
+
+- Pass those values to `agent.start` method, such as:
+
+```typescript
 agent.start({
-  serviceName: '',
-  serviceInstance: '',
-  collectorAddress: '',
-  authorization: '',
-  maxBufferSize: 1000,
+  serviceName: 'my-service-name',
+  serviceInstance: 'my-service-instance-name',
+  collectorAddress: 'my.collector.address:port',
 });
 ```
 
+note that all options given (including empty/null values) will override the corresponding default values, e.g. `agent.start({ collectorAddress: '' })` will override the default value of `collectorAddress` to empty string, causing errors like `DNS resolution failed`.
+
+- Use environment variables.
+
 The supported environment variables are as follows:
 
 Environment Variable | Description | Default